U.S. patent application number 15/034146 was filed with the patent office on 2016-09-22 for method for producing substrates for superconducting layers.
The applicant listed for this patent is DANMARKS TEKNISKE UNIVERSITET. Invention is credited to Anders Christian Wulff.
Application Number | 20160276067 15/034146 |
Document ID | / |
Family ID | 49674174 |
Filed Date | 2016-09-22 |
United States Patent
Application |
20160276067 |
Kind Code |
A1 |
Wulff; Anders Christian |
September 22, 2016 |
METHOD FOR PRODUCING SUBSTRATES FOR SUPERCONDUCTING LAYERS
Abstract
There is provided a method for producing a substrate suitable
for supporting an elongated superconducting element, wherein one or
more elongated strips of masking material are placed on a solid
element (202) so as to form one or more exposed elongated areas
being delimited on one or two sides by elongated strip of masking
material, and placing filling material on the solid element so that
each exposed elongated area within the one or more exposed
elongated areas is covered by a portion of filling material
(318a-c) where each portion of filling material also covers at
least a portion of the adjacent elongated strip of masking material
and subsequently removing the one or more elongated strips of
masking material so as to form one or more corresponding undercut
volumes, where each undercut volume within the one or more undercut
volumes is formed along a portion of filling material and between
the portion of filling material and the solid element. The method
may further comprise placing buffer material (640) and or
superconducting material (642, 644, 646)) on the substrate, so as
to provide a superconducting structure (601) with reduced AC
losses.
Inventors: |
Wulff; Anders Christian;
(Smorum, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DANMARKS TEKNISKE UNIVERSITET |
Kgs. Lyngby |
|
DK |
|
|
Family ID: |
49674174 |
Appl. No.: |
15/034146 |
Filed: |
November 20, 2014 |
PCT Filed: |
November 20, 2014 |
PCT NO: |
PCT/DK2014/050395 |
371 Date: |
May 3, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 5/48 20130101; H01B
12/10 20130101; H01L 39/04 20130101; H01L 39/248 20130101; C25D
5/12 20130101; C25D 5/14 20130101; C25D 5/40 20130101; H01L 39/2454
20130101; H01B 12/06 20130101; C25D 3/38 20130101; C25F 3/02
20130101; H01L 39/126 20130101; H01B 13/0009 20130101; H01B 13/008
20130101; C25D 3/12 20130101; H01L 39/143 20130101; C25D 5/022
20130101 |
International
Class: |
H01B 12/10 20060101
H01B012/10; H01L 39/04 20060101 H01L039/04; H01L 39/12 20060101
H01L039/12; H01B 12/06 20060101 H01B012/06; C25D 3/12 20060101
C25D003/12; C25D 5/14 20060101 C25D005/14; C25D 5/40 20060101
C25D005/40; C25D 5/48 20060101 C25D005/48; C25D 5/02 20060101
C25D005/02; C25D 5/12 20060101 C25D005/12; C25D 3/38 20060101
C25D003/38; C25F 3/02 20060101 C25F003/02; H01B 13/00 20060101
H01B013/00; H01B 13/008 20060101 H01B013/008; H01L 39/24 20060101
H01L039/24 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 2013 |
EP |
13193734.4 |
Claims
1. A method for producing a substrate suitable for supporting an
elongated superconducting element, the method comprising: providing
a solid element, placing one or more elongated strips of masking
material on the solid element, where the one or more elongated
strips of masking material are arranged so as to form one or more
exposed elongated areas, where each exposed elongated area within
the one or more exposed elongated areas is delimited on one or two
sides by at least one elongated strip of masking material within
the one more elongated strips of masking material, placing filling
material on the solid element so that each exposed elongated area
within the one or more exposed elongated areas is covered by a
portion of filling material, where each portion of filling material
also covers at least a portion of the adjacent elongated strip of
masking material, and removing the one or more elongated strips of
masking material so as to form one or more corresponding undercut
volumes, where each undercut volume within the one or more undercut
volumes is formed along a portion of filling material and between
the portion of filling material and the solid element.
2-20. (canceled)
21. The method for producing a substrate suitable for supporting an
elongated superconducting element according to claim 1, wherein the
step of: placing one or more elongated strips of masking material
on the solid element, where the one or more elongated strips of
masking material are arranged so as to form one or more exposed
elongated areas, where each exposed elongated area within the one
or more exposed elongated areas is delimited on one or two sides by
at least one elongated strip of masking material within the one
more elongated strip of masking material, comprises: placing a
plurality of elongated strips of masking material on the solid
element, where adjacent elongated strips of masking material within
the plurality of elongated strips of masking material are arranged
so as to form a plurality of exposed elongated areas, where each
exposed elongated area within the one or more exposed elongated
areas is formed adjacent to at least one elongated strip of masking
material, and wherein one or more exposed elongated areas within
the plurality of exposed elongated areas is formed between adjacent
elongated strips of masking material.
22. The method for producing a substrate suitable for supporting an
elongated superconducting element according to claim 21, where
adjacent elongated strips of masking material within the plurality
of elongated strips of masking material are substantially parallel
with each other.
23. The method for producing a substrate suitable for supporting an
elongated superconducting element according to claim 1, wherein the
solid element is an ellipsoidal cylinder.
24. The method for producing a substrate suitable for supporting an
elongated superconducting element according to claim 21, wherein a
distance between adjacent elongated strips of masking material
within the plurality of elongated strips of masking material is
within 1 micrometer-10 millimeter.
25. The method for producing a substrate suitable for supporting an
elongated superconducting element according to claim 1, wherein a
distance is given between a plane being tangential to upper
surfaces of the one or more portions of filling material after the
step of: removing the one or more elongated strips of masking
material so as to form one or more corresponding undercut volumes,
where each undercut volume within the one or more undercut volumes
is formed along a portion of filling material and between the
portion of filling material and the solid element, and a plane
being tangential to bottoms of volumes bounded on at least two
sides by the solid element and one or more adjacent portions of
filling material, and wherein said distance is large enough so as
to enable that a superconducting material placed on the substrate
may have portions on the bottoms of volumes bounded on at least two
sides by the solid element and one or more adjacent portions of
filling material, and/or on the one or more portions of filling
material, which portions of superconducting material are physically
separated.
26. The method for producing a substrate suitable for supporting an
elongated superconducting element according to claim 1, wherein the
method further comprises placing a layer of buffer material on the
one or more portions of filling material and/or on one or more
sides of the volumes bounded on at least two sides by the solid
element and one or more adjacent portions of filling material.
27. A method for producing an elongated superconducting element,
wherein the method comprises: producing a substrate suitable for
supporting an elongated superconducting element according to claim
1, and wherein the method further comprises placing a layer of
superconducting material on the one or more portions of filling
material and/or on a bottom of volumes bounded on at least two
sides by the solid element and one or more adjacent portions of
filling material, so that the undercut volumes serve to physically
separate individual lines of superconducting material.
28. The method for producing an elongated superconducting element,
wherein the method comprises: producing a substrate suitable for
supporting an elongated superconducting element according to claim
1, and wherein the method further comprises placing, a layer of
buffer material on the one or more portions of filling material
and/or on bottoms of volumes bounded on at least two sides by the
solid element and one or more adjacent portions of filling
material, of the substrate suitable for supporting an elongated
superconducting element, and a layer of superconducting material on
the buffer material, so that the undercut volumes serve to
physically separate individual lines of superconducting material
and/or buffer material.
29. The method for producing an elongated superconducting element
according to claim 27, wherein the step of placing a layer of
superconducting material and/or a layer of buffer material is a
line-of-sight process.
30. A substrate suitable for supporting an elongated
superconducting element, the substrate comprising: a solid element,
and a plurality of portions of filling material on the solid
element and arranged so that a plurality of undercut volumes is
formed along each portion of filling material and between the
portion of filling material and the solid element, wherein a length
of the substrate is at least 1 m.
31. The substrate suitable for supporting an elongated
superconducting element according to claim 30, wherein the
substrate is a tape.
32. The substrate suitable for supporting an elongated
superconducting element according to claim 30, wherein the filling
material is a homogeneous material.
33. The substrate suitable for supporting an elongated
superconducting element according to claim 30, comprising a
plurality of portions of filling material being substantially
parallel and wherein one or more portions of a surface of the solid
element upon which the filling material is placed, said one or more
portions of said surface being placed between said portions of
filling material, is/are substantially planar.
34. The substrate suitable for supporting an elongated
superconducting element according to claim 30 comprising a
plurality of portions of filling material that is substantially
parallel, wherein a surface of the solid element upon which the
filling material is placed, is substantially planar.
35. The substrate suitable for supporting an elongated
superconducting element according to claim 30, wherein the
substrate is a tape, wherein the length of the substrate is at
least 1 m, wherein the filling material is a homogeneous material,
wherein said substrate comprises a plurality of portions of filling
material that are substantially parallel, and wherein one or more
portions of a surface of the solid element, upon which the filling
material is placed, said one or more portions of said surface is
placed between said portions of filling material, is/are
substantially planar.
36. An elongated superconducting element comprising: A substrate
according to claim 30, and a superconducting layer placed on the
substrate or on a buffer on the substrate, so that the undercut
volumes physically separates individual lines of superconducting
material or so that the undercut volumes serve to physically
separate individual lines of superconducting material and/or buffer
material.
37. The elongated superconducting element according to claim 36
incorporated within a performance magnetic coil, a transformer, a
generator, a motor, an electro-motor, a magnetic resonance scanner,
a cryostat magnet, a large hadron collider, an AC power grid cable,
a DC power grid cable, or a smart grid a tokamak .
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for producing
substrates, and in particular relates to substrates suitable for
supporting an elongated superconducting element, and a
corresponding method for producing and using such substrates.
BACKGROUND OF THE INVENTION
[0002] Superconducting structures may be seen as advantageous since
they enable conducting current without resistive losses.
Superconducting structures, such as superconducting tapes are thus
being used for a number of applications, such as generators and
transformers. However, although they possess excellent properties
when carrying direct current, they may exhibit high losses when
used in alternating current (AC) applications.
[0003] Means of reducing AC losses that are currently available may
not in a straightforward manner be adapted to processing long
lengths of superconducting tape.
[0004] In the application U.S. Pat. No. 7,593,758 B2 there is
presented a tape which has a high temperature superconductor layer
that is segmented. Disruptive strips, formed in one of the tape
substrate, a buffer layer, and the superconducting layer create
parallel discontinuities in the superconducting layer that separate
the current-carrying elements of the superconducting layer into
strips or filament-like structures. Segmentation of the current
carrying elements has the effect of reducing AC losses. Methods of
making such a superconducting tape and reducing AC losses in such
tapes are also disclosed.
[0005] In the application U.S. Pat. No. 4,101,731 there is
presented a composite multifilament superconducting structure is
provided, which includes an elongated substrate-carrying,
longitudinally-directed, sputtered discrete filament of an A-15
type intermetallic superconductor. In a preferable procedure, a
plurality of spaced, generally longitudinal grooves are formed on
the surface of an elongated filamentary substrate, preferably a
metal wire. The walls of the grooves on the substrate surface are
shaped to undercut the curvilinear surface of the substrate located
between two adjacent grooves so that at least some of the wall
portions of the grooves are geometrically shadowed during the
subsequent sputtering step in which a superconductor is sputtered
onto the substrate. In particular, a film of a suitable
superconducting intermetallic compound having A-15 crystalline
structure, such as Nb.sub.3Ge, is thereupon sputtered onto the
grooved substrate and deposits at the bottom of the grooves and at
the surface portions of the substrate between grooves. The shadowed
wall portions remain substantially deposit-free so that the
resultant spaced deposits extend as distinct lines or bands along
the substrate to thereby constitute the superconductive filaments.
A plurality of such substrates may, if desired, be consolidated
into a further composite structure, by bundling the substrates and
passing same through a molten metal. The resultant structure may
then be sized to yield as a foral product a composite of the
substrates bearing the superconducting filaments in a surrounding
matrix of the metal.
SUMMARY OF THE INVENTION
[0006] It may be seen as a problem with the prior art methods that
they are not adaptable to continuous processing of long lengths of
such tape, effective, cheap, enabling low material consumption
and/or provides a good substrate for a superconducting tape. It
would be advantageous to have a method for making a substrate for a
superconducting tape having reduced AC losses, wherein the method
is adaptable to continuous processing of long lengths of such tape
and which method would be effective, cheap and/or would be a method
which provided an improved substrate for a superconducting tape
compared to the prior art.
[0007] It may be seen as an object of the present invention to
provide a method of making a substrate for a superconducting tape
having reduced AC losses which is adaptable to continuous
processing of long lengths of such tape and which method is
effective, cheap and/or which provides an improved substrate for a
superconducting tape that solves the above mentioned problems of
the prior art.
[0008] It is a further object of the present invention to provide
an alternative to the prior art.
[0009] Thus, the above described object and several other objects
may be obtained in a first aspect of the invention by providing a
method for producing a substrate suitable for supporting an
elongated superconducting element, such as a superconducting tape
having reduced AC losses, the method comprising, such as comprising
the steps of: [0010] Providing a solid element, such as a solid
nickel based alloy, such as a solid nickel or copper or chrome
based alloy, [0011] Placing one or more elongated strips of masking
material, such as Kapton.RTM. tape or scotch tape or imprint resist
or photoresist, on the solid element, where the one or more
elongated strips of masking material are arranged so as to form one
or more exposed elongated areas, where each exposed elongated area
within the one or more exposed elongated areas is delimited on one
or two sides by at least one elongated strip of masking material,
such as one elongated strip of masking material, such as two
adjacent elongated strips of masking material, within the one more
elongated strips of masking material, [0012] Placing, such as
placing via electrodeposition or via electroplating or via IBAD or
via dip-coating, such as via dip coating in combination with
selective surface treatment or via ink-jet printing or via
electroforming, filling material, such as nickel, such as placing
nickel via electrodeposition, on the solid element so that each
exposed elongated area within the one or more exposed elongated
areas is covered by a portion of filling material, such as covered
by a coherent portion of filling material, where each portion of
filling material also covers at least a portion of the adjacent
elongated strip of masking material, such as one or both of the
adjacent elongated strips of masking material, [0013] Removing,
such as removing by etching or electroetching or dissolving, the
one or more elongated strips of masking material so as to form one
or more corresponding undercut volumes, where each undercut volume
within the one or more undercut volumes is formed along a portion
of filling material and between the portion of filling material and
the solid element.
[0014] The invention is particularly, but not exclusively,
advantageous for obtaining a method for producing a substrate
suitable for supporting an elongated superconducting element, which
method enables employing a large number of solid element materials,
i.e., the method enables choosing between many different materials
for the lower layer, since the material properties of the lower
layer are not decisive in terms of enabling achieving the
undercuts. Another advantage may be that the method enables
choosing between many different materials for the filling material.
For example, the filling material may be a material suitable for
functioning as buffer layer, such as a dip-coated buffer layer,
which may be advantageous in that the portions of the filling
material may immediately be ready for deposition of a
superconducting layer after removal of the one or more elongated
strips of masking material (or maybe even before removal of the
masking material). Furthermore, the substrate generated by the
method enables efficiently separating closely spaced lines of
superconducting material.
[0015] Another possible advantage of the present invention may be
that it enables are large degree of control over the geometry of
the substrate, such as the geometry of the portion(s) of the
filling material adjacent to the undercut volumes. For example, the
undercut volumes may be round, rectangular, triangular or other
shapes designed by the user and have different proportions and
aspect rations depending on the desires of the designer.
[0016] The gist of the invention may be seen as providing a method
which in a few relatively simple steps enables providing a
substrate which may be turned into a superconducting structure,
such as a superconducting tape, having reduced AC losses. The basic
insight underlying the invention may be described as the insight
that undercut volumes (such as undercut volumes in a structure,
such as between the solid element and the one or more portions of
filling material) may be useful for separating layers of material
which are positioned on top of the structure which comprises the
undercut volumes, and that the undercut volumes may be formed by
removal of the elongated strips of masking material so as to leave
behind the filling material which is shaped, such as shaped by the
masking material, so that undercuts may be formed between the one
or more portions of filling material and the solid element. Thus,
relatively simple steps, for example placement of masking strips,
placement of filling material (at least partially on top of the
masking material thereby enabling forming the undercuts), may be
employed in combination so that a solution to the technical problem
of `providing a method which in a few relatively simple steps
enables providing a substrate which may be turned into a
superconducting structure, such as a superconducting structure with
a striated superconductor` may be achieved. The superconducting
element or superconducting structure may be realized by, e.g.,
depositing a layer of superconducting material on top of the solid
element wherein undercuts have been formed along portions of
filling material. The undercuts serve to physically separate the
superconducting material on each portion of filling material, and
superconducting material next to portions of filling material, such
as between adjacent portions of filling material, thereby
effectively forming a striated superconducting layer. The undercuts
may furthermore serve to physically separate both the
superconducting material and additionally deposited layers, such as
shunt and/or capping layers, on each portion of filling material,
and superconducting material next to portions of filling material,
such as between adjacent portions of filling material, thereby
effectively forming a striated superconducting layer.
[0017] The method is furthermore applicable, such as well-suited,
for large-scale manufacturing, since it is a relatively simple
procedure to, e.g., place elongated strips of masking material on a
solid element, place filling material on the exposed elongated
areas next to the strips of masking material and partially on the
masking material, and remove the masking material, even on a large
scale.
[0018] Thus, large scale manufacturing is possible with embodiments
of the invention, and furthermore, this is possible while
minimizing material costs.
[0019] Embodiments of the invention may furthermore be seen as cost
effective, which is in contrast to, e.g., laser stripping which is
not considered cost effective. It may also be seen as an advantage
over laser stripping that embodiments of the present invention
might not suffer from redeposition of stripped material.
Embodiments of the invention may furthermore be seen as effective
in terms of enabling providing substrates for superconducting
structures facilitating relatively large critical currents because
there will be little or no damage zones and/or because an effective
width of the superconductor may be enlarged corresponding to a
width of the solid element (since superconducting layers deposited
on and between one or more portions of filling material may
partially overlap each other). Furthermore, alternative techniques
may generally yield a damage zone, i.e. a portion of
superconducting material which is no longer functional, after
striating the superconducting element, which is in turn reducing
the critical current of the striated superconductor.
[0020] It may be understood that the steps are not necessarily
arranged in the order in which they are to be carried out. In some
embodiments, however, the steps are arranged in the order in which
they are to be carried out.
[0021] By `a substrate suitable for supporting an elongated
superconducting element` is understood a solid element upon which a
superconducting material may be placed, such as deposited, so that
the substrate and the superconducting element may together form an
elongated superconducting element. By elongated superconducting
element is understood a superconducting element which is able to
conduct current a distance in a direction, where the distance is
longer, such as significantly longer, such as 2, 5, 10, 100, 1.000,
10.000 or 100.000 times longer than the width of the conductor in a
direction orthogonal to the direction in which current is
conducted. The length of the substrate may be at least 1 m, such as
at least 10 m, such as at least 100 m, such as at least 1 km, such
as at least 10 km, such as at least 100 km, such as at least 100
km. It may be understood, that the lengths of one or more or all of
the elements optionally placed on the substrate, such as elongated
strips of masking material, filling material, buffer,
superconducting material, shunt layer may have a length being
similar to or identical to the length of the substrate.
[0022] It may be understood that the method may be carried out on a
side of a solid element, such as on a single side or multiple sides
of the solid element (such as on one or both sides of a solid
element being a tape, such as on one or two or three sides of a
solid element having a triangular shape, such as on 1-n sides of a
solid element having a n-polygonal shape). Carrying out the method
on multiple sides of a solid element may be beneficial for enabling
providing a superconductor capable of carrying more current.
[0023] In a particular embodiment, the substrate is a `tape`, i.e.,
an element which has thickness (length along a first dimension)
which is significantly smaller, such as 10, 100 or 1000 times
smaller, than its width (length along a second dimension) and where
the width is significantly smaller, such as 10, 100, or 1.000 times
smaller, than its length (length along a third dimension).
[0024] By `solid element` may be understood an element comprising a
solid phase, such as consisting of a solid phase. The solid element
may be a planar solid element, such as a tape. The solid element
may also have other shapes, where shapes are understood as the
geometrical form as seen in a cross-section in a plane being
orthogonal to a length axis (such as corresponding to an axis
parallel with a direction in which current is to be carried), such
as an arbitrary shape, such as any one of a tape-shape, a
rectangular shape (such as a quadratic shape), a triangular shape,
an ellipsoidal shape (such as a circular shape). The solid element
may comprise any material selected from the group comprising: a
nickel based alloy, a copper based alloy, a chrome based alloy,
iron, aluminum, silicon, titanium, tungsten (also known as wolfram
(W)), silver, hastelloy, and stainless steel.
[0025] By `hastelloy` is understood an alloy wherein the
predominant alloying ingredient is nickel and wherein other
alloying ingredients are added, such as the alloy comprising
varying percentages of one or more of, such as all of, the
elements: molybdenum, chromium, cobalt, iron, copper, manganese,
titanium, zirconium, aluminium, carbon, and tungsten. In a
particular embodiment, hastelloy is an alloy which comprises the
elements Ni, Cr, Fe, Mo, Co, W, C. In a more particular embodiment,
the alloy also comprises Ni, Cr, Fe, Mo, Co, W, C and one or more
of the elements Mn, Si, Cu, Ti, Zr, Al and B. In a more particular
embodiment, the alloy is understood to comprise approximately 47 wt
% Ni, 22 wt % Cr, 18 wt % Fe, 9 wt % Mo, 1.5 wt % Co, 0.6 wt % W,
0.10 wt % C, less than 1 wt % Mn, less than 1 wt % Si and less than
0.008 wt % B. Hastelloy may be referred to as "superalloy" or a
"high-performance alloy" within the art.
[0026] `Stainless steel` is generally known in the art. In
particular embodiments, there is provided stainless steel with
nickel and/or chromium, such as to provide a stainless steel which
is corrosion and/or oxidation resistant, mechanically stable and
non-magnetic at the operation temperature of the superconducting
layer.
[0027] By `elongated` may be understood as referring to something
having a larger dimension in a first direction (such as the
direction referred to as the length direction), such as
significantly longer, such as 2, 5, 10, 100, 1.000, 10.000 or
100.000 times longer than the dimension in one or both of the other
two directions (such as the directions referred to as width and
height) orthogonal to the first direction. The length may be at
least 1 m, such as at least 10 m, such as at least 100 m, such as
at least 1 km, such as at least 10 km, such as at least 100 km,
such as at least 100 km. The length may in particular embodiments
be 1 m, such as 100 m, such as 1 km, such as 20 km, such as 100 km,
such as above 100 km, such as within 1 m-30 km, such as within 1
km-30 km.
[0028] By `one or more elongated strips of masking material` may be
understood an elongated element which may serve the purpose of
masking the solid element. `Masking` is understood as is common in
the art. The masking material may comprise any material selected
from the group comprising: Kapton.RTM. tape, scotch tape, wax,
laquer, imprint resist, polymer and photoresist. An advantage of
using Kapton.RTM. tape or scotch tape may be that it offers a
relatively simple process, e.g., as an alternative to, e.g.,
lithographic techniques which may not applicable for large scale
manufacturing as a photo-resist has to be coated, exposed to e.g.
UV-light and following developed to produce masking strips.
[0029] Throughout this application, it is understood that
`Kapton.RTM. film` refers to the well-known product from DuPont.TM.
which is a film of poly(4,4'-oxydiphenylene-pyromellitimide).
Kapton.RTM. film and Kapton.RTM. tape are used interchangeably.
[0030] By `placing one or more elongated strips of masking
material` may be understood any process resulting in a masking
material being placed onto the solid element, so as to mask the
solid element and thereby forming one or more exposed elongated
areas'. The process of `placing one or more elongated strips of
masking material` may comprise a process chosen from the group
comprising: ink-jet printing (such as ink-jet printing selectively
in areas which are not supposed to become exposed elongated areas).
Alternatively, the step of placing one or more elongated strips of
masking material on the solid element, may be embodied by placing a
film, such as a Kapton.RTM. film, a wax or a lacquer on top of the
solid element. In different embodiments, the strips (i.e., strips
of masking material) may be formed before and/or after the film or
layer, such as a coherent film or layer, is placed on the solid
element. In other words, the elongated strips may be placed on the
solid element as elongated strips, but it may also be conceivable,
that a coherent film or layer is placed on the solid element, and
where portions of the film or layer are subsequently removed so as
to leave behind the elongated strips of masking material. For
example, a striated layer of masking material comprising a
plurality of elongated strips of masking material, may be provided,
e.g., by means of a plurality of strips of Kapton.RTM. film which
are placed onto the solid element, such that the areas between the
strips of Kapton.RTM. film form exposed elongated areas. In another
possible embodiment `placing one or more elongated strips of
masking material` may be carried out using solution planarization
deposition.
[0031] It may be understood that masking material, such as a
coherent masking material, such as a completely covering masking
material, may be placed on parts of the solid element, which parts
are not covered by elongated strips of masking material or
correspond to exposed elongated areas. For example, in case the
solid element is a relatively flat element, such as a tape, a
coherent masking material may be placed on a lower (back-)side of
the solid element, so as to protect this side and/or to avoid that
filling material is deposited there.
[0032] In another example, the `placing one or more elongated
strips of masking material` comprises placing a coherent masking
material on the solid element, and removing masking materials above
the areas corresponding to the exposed elongated areas by a removal
process comprising, e.g., a process chosen from the group
comprising: a cutting process, a scratching process, a rolling
process, a grinding process and a polishing process. By a
`scratching process` is understood that a portion of the upper
layer and possibly a portion of the lower layer is scratched off,
such as scraped off. By `a grinding process` is understood that a
portion of the masking material is removed by a grinding process or
polishing, such as repeatedly scraping off minor portions of the
material to be removed. A `polishing process` is understood to be
similar to a `grinding process` in the present context. By a
`cutting process` is understood a process wherein masking material
is displaced, such as displaced rather than removed. This may be
achieved using a relatively sharp tool, such as a cutting wheel. By
a `rolling process` is understood a process where e.g. masking
material is displaced, such as removed by displacement, such as wax
being displaced.
[0033] By `the one or more elongated strips of masking material are
arranged so as to form one or more exposed elongated areas` may be
understood that elongated areas on the solid element which are not
covered by the masking material, may be referred to as elongated
exposed areas. These areas may be exposed to processes which the
areas covered by the masking material may not be exposed to. It may
be understood that the exposed areas denote fixed areas on the
solid element, i.e., the `exposed areas` may, e.g., in subsequent
steps not be exposed, e.g., after placement of filling material and
removal of the masking material. In other words, the reference to
`exposed areas` (which are used interchangeably with exposed
elongated areas`) may be understood to refer substantially to the
negative of the areas covered by masking material, even after
removal of the masking material.
[0034] By `exposed elongated areas` may be understood `exposed
areas of the solid element` which may be understood as areas of the
solid element which are not covered by masking material, such as
areas between adjacent elongated strips of masking material.
However, an `exposed elongated area` may also be delimited on only
one side by an elongated strip of masking material, and on the
other side by another structural feature, such as an edge of the
solid element. It may be understood that when referring to two
sides of the exposed elongated area, these two sides, are the two
sides in the plane of the surface of the exposed elongated area
which are on either side of the exposed elongated area in a
direction being orthogonal to a length direction of the exposed
elongated area.
[0035] By `each exposed elongated area within the one or more
exposed elongated areas is delimited on one or two sides by at
least one elongated strip of masking material` may be understood
that the elongated exposed areas are delimited on at least one side
by the masking material, but may be delimited on both sides by
masking material, such as two adjacent elongated strips of masking
material. Alternatively, the elongated exposed areas are delimited
on one side by the masking material and on the other side by
another structural element, which may for example be an edge of the
solid element.
[0036] By `placing filling material` may be understood any process
resulting in a solid material being placed onto the exposed
elongated areas, so as to at least partially fill a volume above
the exposed elongated areas which volume extends at least partially
into a volume above the adjacent elongated strip(s) of masking
material. The process of `placing filling material` may comprise a
process chosen from the group comprising: electrodeposition (such
as electrodeposition where the solid element is an electrically
conducting material and the masking material is a less conducting,
such as electrically isolating material), electroplating,
electroforming, Pulsed Laser Deposition, Alternating Beam Assisted
Deposition (ABAD), Ion Beam Assisted Deposition (IBAD) (such as
IBAD leading to material only being deposited primarily, such as
only on the elongated exposed areas), dip-coating (such as
dip-coating in combination with selective surface treatment, such
as selective surface treatment leading to the surface properties of
the exposed elongated areas compared to the surface properties of
the masking material leading to the exposed elongated areas being
more susceptible to deposition compared to the masking material),
and ink-jet printing (such as ink-jet printing selectively in the
exposed elongated areas). It may be understood that the filling
material may be chosed from the group comprising: nickel, chromium,
tungsten, vanadium, aluminum, aluminum oxide (Al.sub.2O.sub.3),
iron, copper, tin, silicon (Si), gadolinium, cobalt, molybdenum,
GdZrO, CeO.sub.2, ZrO, yttrium oxide (Y.sub.2O.sub.3), Yttrium
Stabilished Zirconium and zirconium (Zr). In an embodiment, the
placing of filling material comprises placing nickel via
electrodeposition, such as plating, such as electroplating, on the
solid element. It may in general be noted, that it may be
beneficial that the filling material has a relatively smooth
surface, since this may be beneficial for subsequent deposition and
utilization of superconducting material. In an embodiment, filling
material, such as nickel or chrome, is deposited so as to obtain a
smooth surface, such as by controlling the current density (and
thus the deposition rate) and/or by filtering of the electroplating
solution. It may also be understood that filling material may be
deposited by controlling current density and/or voltage and/or
controlling the temperature of e.g. the plating solution. Various
deposition parameters affecting the surface roughness are described
in each of the following references: A) Metal Finishing, 79th
Surface Finishing Guidebook, Fall 2011 VOLUME 109 NUMBER 11A, ISSN
0026-0576 and B) Rustfrit stal og corrosion, Claus Qvist Jessen, 1.
udgave, 1. oplag 2011, ISBN 978-87-92765-00-0, Forlaget Moller
& Nielsen, which are each hereby incorporated by reference in
entirety. In another possible embodiment `placing filling material`
may be carried out using solution planarization deposition.
[0037] It may be beneficial for the subsequent formation of a
superconducting layer that the surface roughness of the substrate
is relatively low. In order to decrease the surface roughness at
the positions where there is filling material, such as the surfaces
of the portions of filling material, and the substrate in general,
an electropolishing step and/or a buffer layer deposition step can
be conducted in order to decrease the surface roughness compared to
the roughness of the filling material immediately after
electrodeposition, such as electroplating. In one embodiment, the
method comprises an electropolishing step, such as an
electropolishing step which is carried out while the elongated
strips of masking material, such as the Kapton.RTM. tape, is still
present (i.e., the elongated strips of masking material are not
removed from the solid element until the electropolishing step has
been carried out), so as to decrease the surface roughness, so as
to decrease the surface roughness in order to facilitate improved
properties of the substrate in terms of enabling a higher quality
of a subsequently deposited superconducting layer.
[0038] Generally, for any embodiment of the present invention, the
surface (RMS) roughness of the solid element and/or the portions of
filling material, may be below 100 nm, such as below 50 nm, such as
below 25 nm, such as below 20 nm, such as below 15 nm, such as
below 10 nm, such as below 5 nm, such as below 1 nm. An advantage
of this may be, that it facilitates having improved properties of a
superconducting material which is subsequently placed, such as
deposited, on the solid element and/or the portions of filling
material.
[0039] By `so that each exposed elongated area within the one or
more exposed elongated areas is covered by a portion of filling
material` may be understood that each exposed area is covered by a
portion of filling material, such as completely covered by a
portion of filling material, such as completely covered by a
coherent portion of filling material. By `a coherent portion of
filling material` may be understood that the portion of filling
material forms one coherent piece of solid material.
[0040] By `where each portion of filling material also covers at
least a portion of the adjacent elongated strip of masking
material` may be understood that the portion of filling material
which covers an exposed elongated area, also covers at least a
portion of the adjacent elongated strip of masking material, such
as one or both of the adjacent elongated strips of masking
material, so that the portion of filling material covers both the
exposed area and a portion of masking material. In other words, at
least a portion of the masking material is below a portion of
filling material.
[0041] In an embodiment, the portion of filling material covers
only a portion (but not all) of the elongated strip of masking
material, such as the portion of filling material covers only a
fraction of the masking material, such as covers the edge of
masking material (between the masking material and the exposed
area), but not all of the masking material in a direction away from
the exposed elongated area (as illustrated in the exemplary
embodiment shown in FIG. 4). An advantage of this may be, that the
masking material is thus relatively easily accessible by, e.g., an
etchant or a solvent. Another advantage may be that the masking
material may relatively easily be removed, since it is not
completely covered by filling material.
[0042] By `Removing the one or more elongated strips of masking
material` may be understood that the masking material is partially
or completely removed from the structure comprising the solid
element and filling material. The removal may be carried out by any
process selected from the group comprising: etching, dissolving,
peeling and evaporation, or combinations thereof. The removal may
be carried out by a process wherein the one or more elongated
strips of masking material are attached to the solid element via an
adhesive, and wherein the step of removing the one or more
elongated strips of masking material comprises dissolving the
adhesive, such as a protective tape glue, and peeling of the one or
more elongated strips of masking material. For example, in case the
masking material is Kapton.RTM. tape, then the glue on the
Kapton.RTM. tape may be dissolved by, e.g., ethanol and/or acetone
and thereby enabling relatively easy removal of the Kapton.RTM.
tape by peeling of the Kapton.RTM. tape.
[0043] By `etching (the masking material)` may be understood that
the elongated strips of masking material are etched with an
etchant. The etchant may in particular embodiments be in any one of
the following states of matter: plasma, liquid and gas. In a
particular embodiment Reactive Ion Etching (RIE) is employed.
[0044] By `form one or more corresponding undercut volumes` may be
understood a process wherein the removal of masking material may
lead to the forming of undercut volumes. By `corresponding undercut
volumes` may be understood that an undercut volume corresponds to a
volume which previously (before removal of masking material)
corresponded to a volume occupied by masking material. It may be
understood that one strip of masking material may correspond to one
or two undercut volumes.
[0045] By `each undercut volume within the one or more undercut
volumes is formed along a portion of filling material and between
the portion of filling material and the solid element` may be
understood that the undercut volumes are formed next to a portion
of filling material, such as below a sub-portion of filling
material which sub-portion of filling material is next to an edge
of a portion of filling material, and extends in the same direction
as the portion of filling material.
[0046] In terms of directions, it is understood when referring to
`up` that an up-down axis is defined as being in a direction
orthogonal to the surface of the solid element, such as the surface
of the solid element upon which the masking material and/or the
filling material may be placed, and that `up` is in the direction
from the surface of the solid element and away from the solid
element, and vice versa for the direction `down`, i.e., `down` is
the direction from the surface of the solid element and into the
solid element. It is understood that the up-down axis is parallel
to a y-axis as indicated in the figures, and that `up` is in the
positive y-direction. This definition of direction also applies
when using the terms `above` and `below` which are given their
general meaning. It is noted that the surface of the solid element
may not necessarily be planar, in which case the up-down axis
remains orthogonal to the surface, and where it is understood that
an up-down axis corresponding to one position on the surface need
not necessarily be parallel with an up-down axis corresponding to
another position on the surface.
[0047] By `undercut volume` is understood a volume where no solid
material is present, which volume may be below a remaining portion
of filling material. Thus an undercut volume may be above the
surface of the solid element while still shadowed by an overhanging
portion of filling material. Thus, when a material is deposited on
the sandwich comprising the solid element and the portion(s) of
filling material, (or the portion(s) of filling material after
removal of the elongated strips of masking material), using a
line-of-sight process for deposition of material in a direction
following the up-down-axis from a position above the sandwich
comprising the solid element and the portion(s) of filling material
(such as the up-down axis being orthogonal to the surface of the
solid element at the position of the undercut volume), and undercut
volume(s) are present, then the material is not deposited on the
portion(s) of the filling material and solid element which borders
the undercut volumes, such as which is respectively directly above
and below the undercut volume(s).
[0048] The invention may in particular embodiments encompass having
one or more intermediate layers of material inserted between a bulk
portion of the solid element and the elongated strips of masking
material, such as having one or more intermediate layers separating
the a bulk portion of the solid element and elongated strips of
masking material, such as the one or more intermediate layer
functioning as a barrier for any one of heat, current and diffusion
of atoms, ions and/or molecules between the bulk portion of the
solid element and the elongated strips of masking material. In that
case, it may be understood that the solid element includes the bulk
portion of the solid element, and the intermediate layer, such that
an element placed on the intermediate layer is understood to be
placed on the solid element. An advantage of having one or more
intermediate layers may be that it improves the mechanical
properties, such as making the layered solid element stronger or
more rigid.
[0049] It may be understood, that there may be one or more
elongated strips of masking material, such as 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 50, 100 or 1000 elongated strips of masking material. It
may be understood, that there may be one or more exposed elongated
areas, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 50, 100 or 1000
exposed elongated areas. It may be understood, that an elongated
strip of masking material may border 1 or 2 exposed elongated
areas. It may be understood that an exposed elongated area may
border 1 or 2 elongated strips of masking material. Thus, it is
conceivable to have embodiments with 1 elongated strip of masking
material and 1 exposed elongated area, 2 elongated strips of
masking material and 1 exposed elongated area, 2 elongated strips
of masking material and 2 exposed elongated areas, 2 elongated
strip of masking material and 3 exposed elongated areas, 1
elongated strip of masking material and 2 exposed elongated areas,
and so forth. For example, for a 4 mm wide solid element, it may be
possible to have from one side to the other: 1 mm masking material,
1 mm exposed area (bordered on both sides by masking material), 1
mm masking material, 1 mm exposed area (bordered by masking
material on one side and the edge of the solid element on the
other.
[0050] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element, wherein the step of [0051] Placing one or more elongated
strips of masking material, such as Kapton.RTM. tape or scotch tape
or imprint resist or photoresist, on the solid element, where the
one or more elongated strips of masking material are arranged so as
to form one or more exposed elongated areas, where each exposed
elongated area within the one or more exposed elongated areas is
delimited on one or two sides by at least one elongated strip of
masking material, such as one elongated strip of masking material,
such as two adjacent elongated strips of masking material, within
the one more elongated strip of masking material, [0052] comprises
[0053] Placing a plurality of elongated strips of masking material,
such as Kapton.RTM. tape or scotch tape or imprint resist or
photoresist, on the solid element, where adjacent elongated strips
of masking material within the plurality of elongated strips of
masking material are arranged so as to form one or more exposed
elongated areas, where each exposed elongated area within the one
or more exposed elongated areas is formed adjacent to at least one
elongated strip of masking material.
[0054] According to this embodiment, there is provided a plurality
of elongated strips of masking material, such as 2, 3, 4, 5, 6, 7,
8, 9, 10, 50, 100 or 1000 elongated strips of masking material, and
at least one exposed area, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
50, 100 or 1000 exposed elongated areas.
[0055] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element, wherein the step of [0056] Placing one or more elongated
strips of masking material, such as Kapton.RTM. tape or scotch
tape, imprint resist or photoresist, on the solid element, where
the one or more elongated strips of masking material are arranged
so as to form one or more exposed elongated areas, where each
exposed elongated area within the one or more exposed elongated
areas is delimited on one or two sides by at least one elongated
strip of masking material, such as one elongated strip of masking
material, such as two adjacent elongated strips of masking
material, within the one more elongated strip of masking material,
[0057] comprises [0058] Placing one or more elongated strips of
masking material, such as Kapton.RTM. tape or scotch tape or
imprint resist or photoresist, on the solid element, where the one
or more elongated strips of masking material are arranged so as to
form a plurality of exposed elongated areas, where each exposed
elongated area within the one or more exposed elongated areas is
formed adjacent to at least one elongated strip of masking
material.
[0059] According to this embodiment, there is provided at least one
elongated strip of masking material, such as 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 50, 100 or 1000 elongated strips of masking material, and
a plurality of exposed elongated areas, such as 2, 3, 4, 5, 6, 7,
8, 9, 10, 50, 100 or 1000 exposed elongated areas.
[0060] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element, wherein the step of [0061] Placing one or more elongated
strips of masking material, such as Kapton.RTM. tape or scotch tape
or imprint resist or photoresist, on the solid element, where the
one or more elongated strips of masking material are arranged so as
to form one or more exposed elongated areas, where each exposed
elongated area within the one or more exposed elongated areas is
delimited on one or two sides by at least one elongated strip of
masking material, such as one elongated strip of masking material,
such as two adjacent elongated strips of masking material, within
the one more elongated strip of masking material, [0062] comprises
[0063] Placing a plurality of elongated strips of masking material,
such as Kapton.RTM. tape or scotch tape or imprint resist or
photoresist, on the solid element, where adjacent elongated strips
of masking material within the plurality of elongated strips of
masking material are arranged so as to form a plurality of exposed
elongated areas, where each exposed elongated area within the one
or more exposed elongated areas is formed adjacent to at least one
elongated strip of masking material, and wherein one or more
exposed elongated areas within the plurality of exposed elongated
areas is formed between adjacent elongated strips of masking
material, such as wherein a plurality of exposed elongated areas
within the plurality of exposed elongated areas is formed between
adjacent elongated strips of masking material.
[0064] According to this embodiment, there is provided a plurality
of elongated strips of masking material, such as 2, 3, 4, 5, 6, 7,
8, 9, 10, 50, 100 or 1000 elongated strips of masking material, and
a plurality of exposed elongated areas, such as 2, 3, 4, 5, 6, 7,
8, 9, 10, 50, 100 or 1000 exposed elongated areas.
[0065] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element, where adjacent elongated strips of masking material within
the plurality of elongated strips of masking material are
substantially parallel with each other, such as parallel with each
other. By `parallel` may be understood parallel within 0, 1, 2, 3,
4, 5, 6, 7, 8, 9 or 10 degrees. It may be understood that the
elongated strips may be piecewise parallel, such as the elongated
strips themselves being non-rectilinear, such as curvilinear, such
as piecewise linear, although immediately adjacent sections of
masking material may still be parallel.
[0066] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element, wherein the solid element is an ellipsoidal cylinder, such
as a circular cylinder. It may be understood that the geometric
shape (such as ellipsoidal, such as circular) of the solid element,
may refer to an outer shape of a cross-section of the cylinder,
where the cross-section lies in a plane being perpendicular to the
generating lines. It may be understood, that the solid element may
have a length axis which is not necessarily parallel with the
length axis of the elongated strips of masking material. In an
embodiment, the solid element may have a length axis which is
substantially perpendicular, such as perpendicular to a length axis
of the elongated strips of masking material. This may, for example,
be the case for a cylinder, where the length axis of the elongated
strips of masking material is along a surface of the cylinder
around a center axis of the cylinder along the axis of the
cylinder. In another embodiment, the solid element may have a
length axis which is substantially parallel, such as parallel to a
length axis of the elongated strips of masking material.
[0067] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element, wherein a distance (752) between adjacent elongated strips
of masking material within the plurality of elongated strips of
masking material is within 1 micrometer-10 millimeter, such as 1
micrometer-4 millimeter.
[0068] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element, wherein a distance (752) between adjacent elongated strips
of masking material within the plurality of elongated strips of
masking material is within 1 micrometer-1 millimeter, such as
within 10-100 micrometer, such as within 0.1 nm-10 mm, such as
within 1 nm-1000 micrometer, such as within 1 nm-100 micrometer,
such as within 1 nm-10 micrometer, such as within 10 nm-1000
micrometer, such as within 10 nm-100 micrometer, such as within 10
nm-10 micrometer, such as within 100 nm-1000 micrometer, such as
within 100 nm-100 micrometer, such as within 100 nm-10 micrometer,
such as within 1-1000 micrometer, such as within 1-100 micrometer,
such as within 1-10 micrometer, such as within 10-1000 micrometer,
such as within 20-200 micrometer, such as within 100-1000
micrometer, such as less than 10 micrometer, such as less than 100
micrometer, such as less than 200 micrometer, such as less than
1000 micrometer, such as less than 10 mm. An advantage of having
the distance between adjacent elongated strips of masking material
within this range may be that it enables reducing AC losses. It is
to be understood that the distance between adjacent elongated
strips of masking material is to be measured in a direction being
parallel to the surface of the solid element, and orthogonal to the
direction of the elongated strips of masking material. The adjacent
elongated strips of masking material may in particular embodiments
be substantially parallel, such parallel.
[0069] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element, wherein a distance is given between a plane being
tangential to upper surfaces of the one or more portions of filling
material after the step of [0070] Removing, such as removing by
etching or dissolving, the one or more elongated strips of masking
material so as to form one or more corresponding undercut volumes,
where each undercut volume within the one or more undercut volumes
is formed along a portion of filling material and between the
portion of filling material and the solid element, and a plane
being tangential to bottoms of volumes bounded on at least two
sides, such as three sides, by the solid element and one or more
adjacent portions of filling material, and wherein said distance is
large enough so as to enable that a superconducting material placed
on the substrate may have portions [0071] on the bottoms of volumes
bounded on at least two sides, such as three sides, by the solid
element and one or more adjacent portions of filling material,
[0072] and/or [0073] on the one or more portions of filling
material, which portions of superconducting material are physically
separated, such as physically separated due to the one or more
undercuts. In embodiments, said distance is within 50 nm-10
micrometer, such as within 1-100 micrometer, such as within 0.1 nm
-10 mm, such as within 1 nm-1000 micrometer, such as within 1
nm-100 micrometer, such as within 1 nm-10 micrometer, such as
within 10 nm-1000 micrometer, such as within 10 nm-100 micrometer,
such as within 10 nm-10 micrometer, such as within 0.1-1000
micrometer, such as within 0.1-1000 micrometer, such as within
0.1-100 micrometer, such as within 0.1-10 micrometer, such as
within 1-1000 micrometer, such as within 1-10 micrometer, such as
within 10-1000 micrometer, such as within 10-100 micrometer, such
as less than 10 micrometer, such as less than 100 micrometer, such
as less than 200 micrometer, such as less than 1000 micrometer,
such as less than 10 mm. By said `bottom(s) of volumes` may be
understood the surface portions of the solid element corresponding
to the areas previously occupied by the elongated strips of masking
material, such as the areas adjacent to the portions of filling
material. In embodiments said distance is within 0.1 nm to 1 mm, or
within 50 nm-10 micrometer, or within 1-100 micrometer, or within
0.1 nm -10 mm, or within 1 nm-1000 micrometer, or within 1 nm-100
micrometer, or within 1 nm-10 micrometer, or within 10 nm-1000
micrometer, or within 10 nm-100 micrometer, or within 10 nm-10
micrometer, or within 0.1-1000 micrometer, or within 0.1-1000
micrometer, or within 0.1-100 micrometer, or within 0.1-10
micrometer, or within 1-1000 micrometer, or within 1-10 micrometer,
or within 10-1000 micrometer, or within 10-100 micrometer, or less
than 10 micrometer, or less than 100 micrometer, or less than 200
micrometer, or less than 1000 micrometer, or less than 10 mm.
[0074] The volumes between the portions of filling material may be
referred to as `disruptive strips`. By `disruptive strip` may be
understood a line of lack of filling material, which separates
filling material into elongated strips of filling material on both
sides of the disruptive strip. A disruptive strip may be seen as a
gap in an otherwise coherent filling material. If a coherent
filling material, such as a coherent layer of filling material, is
traversed by a disruptive strip, the continuity of the coherent
filling material is thus disrupted into two separate (layers of)
material, such as two portions of filling material.
[0075] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element wherein a distance between adjacent disruptive strips
within a plurality of disruptive strips is within 0.1 micrometer-10
millimeter.
[0076] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element wherein a distance between adjacent disruptive strips
within a plurality of disruptive strips is within 1 micrometer-1
millimeter In another embodiment, there is provided a method for
producing a substrate suitable for supporting an elongated
superconducting element wherein a width of the disruptive strips
may be 1 micrometer, such as 2 micrometer, such as 5 micrometer,
such as 10 micrometer, such as 30 micrometer, such as 100
micrometer, such as 1 mm, such as 4 mm, such as 5 mm, such as 10
mm, such as within 1 micrometer-1 mm, such as 1 micrometer-10 mm,
such as 1 mm-10 mm. An advantage of having the width in this range
may be that it enables physically separating layers deposited on
the substrate. It is to be understood that the width is to be
measured in a direction being parallel to the surface of the solid
element, and orthogonal to the direction of the disruptive strips,
such as the length direction of the elongated strips of masking
material.
[0077] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element, wherein the method further comprises placing a layer of
buffer material (640) on [0078] the one or more portions of filling
material (318a-c) [0079] and/or on [0080] one or more sides, such
as all solid sides, of the volumes bounded on at least two sides,
such as three sides, by the solid element and one or more adjacent
portions of filling material.
[0081] In an embodiment, there is presented a method for producing
an elongated superconducting element, wherein the method comprises
the steps of producing a substrate suitable for supporting an
elongated superconducting element according to the first aspect,
such as the previously described embodiments, and wherein the
method further comprises placing, [0082] a layer of buffer material
(640) [0083] on the one or more portions of filling material
(318a-c) [0084] and/or [0085] on bottoms of volumes bounded on at
least two sides by the solid element and one or more adjacent
portions of filling material, [0086] of the substrate suitable for
supporting an elongated superconducting element provided according
to the first aspect, such as the previously described embodiments,
and [0087] a layer of superconducting material (642, 644, 646) on
the buffer material, [0088] so that the undercut volumes (332)
serve to physically separate individual lines of superconducting
material and/or buffer material.
[0089] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element, wherein the one or more portions of filling material, and
optionally the substrate, is shaped so as to enable twist pitching,
such as a ROEBEL configuration (cf., the reference "Supercond. Sci.
Technol. 22 (2009) 034003" which is hereby incorporated by
reference in entirety), such as a Conductor On Round Core (cf. the
reference "Supercond. Sci. Technol. 27 (2014) 125008" which is
hereby incorporated by reference in entirety), or such as a
geometry that enables transposition of superconducting elements
placed on said substrate. Said shaping may be given by a piecewise
linear shape, such as a zig-zag shape.
[0090] According to a second aspect of the invention, there is
provided a method for producing an elongated superconducting
element, wherein the method according to the second aspect
comprises the method according to the first aspect and wherein the
method further comprises placing a layer of superconducting
material (642, 644, 646) [0091] on the one or more portions of
filling material (318a-c) [0092] and/or on [0093] a bottom of
volumes bounded on at least two sides, such as three sides, by the
solid element and one or more adjacent portions of filling
material, [0094] so that the undercut volumes (332) serve to
physically separate individual lines of superconducting
material.
[0095] An advantage of placing a layer of superconducting material
on the one or more portions of filling material and/or on the
bottom of volumes may be that it enables providing a
superconducting structure. An advantage of placing a layer of
superconducting material on the one or more portions of filling
material and/or on the bottom of volumes so that the undercut
volumes serve to physically separate individual lines of
superconducting material may be that it enables providing a
plurality of lines of superconducting material which are physically
separated and hence effectively reduce the AC losses. A possible
advantage is that it enables low material consumption, since no
superconducting material need to be removed in order to realize the
physical separation. Furthermore, an advantage may be that it may
enable a complete utilization of the width of the substrate
suitable for supporting an elongated superconducting element since
no material is effectively missing between adjacent parallel lines
of superconducting material. According to a further embodiment,
there is provided a plurality, such as two or more, of elongated
superconducting elements (such as being based on the elongated
substrate according to the first aspect), and they are assembled in
a twist pitching configuration.
[0096] In an embodiment according to the second aspect, there is
provided a method for producing an elongated superconducting
element, wherein the method according to the second aspect
comprises the method according to the first aspect, and wherein the
method further comprises placing, [0097] a. a layer of buffer
material [0098] on the one or more portions of filling material
[0099] and/or [0100] on bottoms of volumes bounded on at least two
sides, such as three sides, by the solid element and one or more
adjacent portions of filling material, [0101] of the substrate
suitable for supporting an elongated superconducting element
provided according to the first aspect, and [0102] b. a layer of
superconducting material on the buffer material, [0103] so that the
undercut volumes serve to physically separate individual lines of
superconducting material and/or buffer material.
[0104] A possible advantage of placing a layer of buffer material
on the one or more portions of filling material and/or on the
bottom of volumes may be that it enables placing a layer of
superconducting material on top of the buffer layer, where the
superconducting properties of the superconducting layers are
improved and/or protected by being placed on the buffer layer, as
opposed to being placed directly on the one or more portions of
filling material and/or on the bottom of volumes. More
specifically, the superconducting material may be improved since
the buffer material may provide a texture which is advantageous in
terms of improving the superconducting properties of the
superconducting material. For example, if a substrate has a
relatively rough substrate, then placing a buffer layer on such
substrate may enable achieving a roughness (of the buffer--and
hence the surface on which a superconducting layer is to be placed)
of, e.g., 0.1 nm.sub.RMS-10 nm.sub.RMS. More specifically, the
superconducting material may be protected since the buffer material
may provide a barrier against potentially harmful elements (in
terms of superconducting properties), such as atoms, ions and/or
molecules which could have diffused from the one or more portions
of filling material and/or on the solid element and into the
superconducting material, and thereby deteriorate the
superconducting properties. An advantage of placing a layer of
superconducting material on the buffer material may be that it
enables providing a superconducting structure. An advantage of
doing it so that the undercut volumes serve to physically separate
individual lines of superconducting material and/or buffer material
may be that it enables providing a plurality of lines of
superconducting material which are physically separated and hence
effectively reduce the AC losses. The thickness of the layer of the
superconducting material (in a direction orthogonal to the plane of
the upper layer and the lower layer) may be 100 nm, such as 1000
nm, such as 3 micrometer, such as 5 micrometer, such as 50
micrometer, such as 100 micrometer, such as within the range of 100
nm-3 micrometer, such as within a range of 100 nm-50 micrometer,
such as within a range of 100 nm-5 micrometer. It is noted that an
advantage of having relatively thin superconducting layers may be
that too thick layers becomes brittle and may fracture upon
bending/winding into e.g. a coil. Very thick superconductor layers
(made of Rare earth based barium copper oxide, such as Yttrium
barium copper oxide, a crystalline chemical compound with the
formula YBa.sub.2Cu.sub.3O.sub.7-x (YBCO)), are known to have a
lower critical current density compared with thinner layers.
Multilayers of YBCO with intermediate buffer layers is one method
for producing an effective thick superconductor stack with an
overall higher critical current. By Rare earth elements is
understood Gd, Nd, Sm, Eu, Ey, Y.
[0105] It is understood, that in order to obtain the advantage of
having electrically decoupling adjacent lines, it may not be
necessary that the lines of layer of material which is
superconducting when placed on the buffer material is itself
physically separated from adjacent lines. It may be sufficient that
lines of buffer material are separated so that the layer of
superconducting material is only superconducting along (and above)
the lines of buffer material, whereas the corresponding lines of
material in between are not superconducting.
[0106] In an embodiment, there is provided a method for producing a
substrate suitable for supporting an elongated superconducting
element, such as a method for producing an elongated
superconducting element, wherein the method further comprises
placing, such as depositing, a layer of superconducting material on
one or more portions of filling material and/or on the bottom of
volumes of the layered solid element so that the undercut volumes
serve to physically separate individual lines of superconducting
material, and the method further comprising placing, such as
depositing, [0107] a layer of buffer material on the
superconducting material, such as on top of the superconducting
material, such as on the side of the superconducting material being
away from the solid element.
[0108] Strong texture and epitaxial growth of e.g. superconducting
YBCO may be difficult to obtain for very thick layers (such as 500
nm-5 .mu.m or more than 5 micrometer or more than 7 .mu.m
thickness). It is noted that texture and epitaxial growth decay at
high superconductor YBCO layer thicknesses. A possible advantage of
placing an (extra) layer of buffer material on the superconducting
material may be that the superconducting properties of an
additional superconducting layer (deposited on top of the extra
buffer layer) may be improved, since the (extra) buffer layer again
increases the fraction of texture and level of epitaxial growth.
Thus, a possible advantage of placing a layer of buffer material on
the superconducting material may be that it enables forming a
`stack` of high quality superconducting films.
[0109] In a further embodiment according to the second aspect,
there is provided a method for producing an elongated
superconducting element, wherein the method according to the second
aspect comprises the method according to the first aspect, wherein
the step of placing, such as depositing, a layer of superconducting
material (642, 644, 646) and/or a layer of buffer material (640) is
a line-of-sight process, such as a physical vapour deposition
process, such as a pulsed laser deposition process, such as RF
sputtering, such as E-beam evaporation, such as Ion Beam Assisted
Deposition (IBAD), such as Alternating Beam Assisted Deposition
(ABAD).
[0110] By a `line-of-sight` process is understood any process which
enables depositing material only on positions of a substrate which
may be seen along a straight line from another position, such as a
position above the substrate. `Line-of-sight` process is thus
construed broadly to comprise processes where the deposited
material follows straight lines prior to deposition and processes
for deposition which has a similar effect. In a particular
embodiment, the line-of-sight process is any one of die coating,
bubble jet coating and ink-jet coating.
[0111] A possible advantage of using a line-of-sight process may be
that it enables depositing material only outside of the undercut
volumes, and thus enables in a simple step to simultaneously
achieve deposition of material outside the undercut volumes and
achieve that there is no deposition of material within the undercut
volumes.
[0112] In particular embodiments, `line-of-sight` is understood to
be a process wherein the deposited material has its origin from a
source and travels in a direct line therefrom to the position where
it is deposited. In other words, there can only be deposited
material on positions from which there can be drawn a straight line
to the source which does not traverse any obstacles. In a
particular embodiment, the source is above the undercut volumes. In
another embodiment, the source is so far above the lower layer,
that virtual lines from the source to different positions on the
substrate, such as positions within the undercut volumes are
substantially parallel.
[0113] In an embodiment according to the second aspect, there is
provided a method for producing an elongated superconducting
element, wherein the method according to the second aspect
comprises the method according to the first aspect and wherein the
method is further comprising placing a shunt layer on the layer of
superconducting material (642, 644, 646).
[0114] By a `shunt layer` is understood a layer of material which
is placed on the layer of superconducting material, which has high
thermal conductivity and high electrical conductivity. An advantage
of having a shunt layer may be, that if the an underlying
superconductor does not conduct well at a certain point, the
current may pass this (low conductivity) point via the (high
conductivity) shunt layer thereby avoiding a failure of the
structure due to resistive heating. Exemplary materials of the
shunt layer may comprise silver (Ag) and/or copper (Cu and/or gold
(Au). The shunt layer is not chemically active with respect to the
layer of superconducting material, or the shunt layer is not
typically chemically active with respect to the layer of
superconducting material. The undercut volumes may be advantageous
with respect to the shunt layer as the undercut volumes associated
with the disruptive strips may also physically separate the shunt
layer, such as physically separate the shunt layer material on
either side of each disruptive strip and shunt layer material
within the disruptive strip, thereby effectively forming a striated
shunt layer, such as turning the shunt layer into stripes of shunt
layer material. An advantage of forming a striated shunt layer may
be that it enables removing high conductivity contact (through the
shunt layer) between the lines of superconducting material, which
is also separated by the undercut volumes, while still being able
to thermally conduct to the outer supporting structure and allowing
current to pass potential points of low conductivity (in parallel
with the normal current direction) thus both enabling normal
cooling and protection of the superconductor in the event of a
quench. The shunt layer may be placed on the superconducting
material with methods known in the art, such as by deposition,
sputter deposition, electrochemical deposition, galvanic
deposition, or similar methods. In alternative embodiments, the
shunt layer is chemically active.
[0115] A capping layer may be understood as a layer yielding
mechanical strength and/or further improving the thermal
properties. A capping layer may typically comprise copper (Cu). It
may in general be understood that the advantages described above in
connection with striation/physical separation may also apply to
capping layers. Thus, it may be seen as advantageous to have
undercuts enabling physical separation of shunt layers and/or
capping layers.
[0116] An advantage of forming a shunt layer and/or capping layer
may be that such layer(s) may function as a mechanically
stabilizing layer and/or as a layer improving the thermal
properties, such as the shunt layer functioning as a thermally
conducting layer, which may, e.g., facilitate conduction excess
heat in case of a thermal quench (which in turn may thus serve to
prevent or avert that a superconductor based on the substrate may
become too hot and possibly even break down or burn due to
overheating).
[0117] In another embodiment, there is provided a method for
producing a substrate suitable for supporting an elongated
superconducting element, such as a method for producing an
elongated superconducting element, wherein the method further
comprises introducing virtual cross-cuts in the substrate, the
buffer layer and/or the superconducting material. Such virtual
transverse cross-cuts may be beneficial for reducing AC loss.
Virtual transverse cross-cuts are described in the reference "AC
Loss Reduction in Filamentized YBCO Coated Conductors With Virtual
Transverse Cross-Cuts", Zhang et al., IEEE TRANSACTIONS ON APPLIED
SUPERCONDUCTIVITY, VOL. 21, NO. 3, Jun. 2011, 3301-3306, which is
hereby incorporated by reference in entirety.
[0118] According to a third aspect of the invention, there is
provided a substrate suitable for supporting an elongated
superconducting element, the substrate comprising: [0119] A solid
element, [0120] One or more portions of filling material on the
solid element and arranged so that a plurality of undercut volumes
is formed along each portion of filling material and between the
portion of filling material and the solid element.
[0121] In an embodiment, there is provided a substrate (300)
suitable for supporting an elongated superconducting element,
wherein the substrate is chosen from the group comprising: tape,
roll, drum and reel. In an embodiment there is provided a substrate
(300) suitable for supporting an elongated superconducting element,
wherein the substrate is a tape.
[0122] In an embodiment, there is provided a substrate suitable for
supporting an elongated superconducting element, comprising a
plurality of portions of filling material, such as at least 3
portions of filling material, wherein a length of the substrate is
at least 1 m, such as at least 10 m, such as at least 100 m, such
as at least 1 km, such as at least 10 km, such as at least 100 km,
such as at least 100 km. An advantage of having a relatively great
length of the substrate may be that it enables forming a
superconductor via the substrate, which enable conducting current
across correspondingly great distances.
[0123] In an embodiment, there is provided a substrate suitable for
supporting an elongated superconducting element, wherein the
filling material is a homogeneous material.
[0124] By `wherein the filling material is a homogeneous material`
may be understood, that the filling material is a homogeneous type
of material, such as the filling material is not a layered material
where structure and/or composition depends on the distance to the
solid element, such as the structure and composition at one
position is similar to structure and composition at another
position (for example the two positions being spatially separated
along an axis being orthogonal to a surface of the solid element),
such as a material which does not differ in one or more of
structure (e.g., degree of crystallinity and/or type of crystal
structure) and/or composition (e.g., chemical composition, such as
elemental composition), such as when going along an axis being
orthogonal to the solid element. It may be understood as is common
in the art, that `homogeneous` encompasses mixtures of materials on
a microscopic scale where the components does not appear in layered
form, for example an alloy might be homogeneous or might contain
small particles, such as components that can be viewed with a
microscope. It may be understood that the wording `wherein the
filling material is a homogeneous material` encompasses embodiments
wherein one or more undercut volumes is formed along said
homogeneous portion of filling material and between the homogeneous
portion of filling material and the solid element (in other words:
Said wording does not exclude that a homogeneous portion of filling
material with an associated undercut is coated with another layer,
(thereby forming a seemingly inhomogeneous structure, e.g., a
layered structure), as long as the homogeneous portion alone forms
a filling material with an associated undercut).
[0125] In an embodiment, there is provided a substrate suitable for
supporting an elongated superconducting element, comprising a
plurality of portions of filling material, such as at least 3
portions of filling material, being substantially parallel, such as
parallel with each other, and wherein one or more portions of a
surface of the solid element, such as an upper surface 314, upon
which the filling material is placed, said one or more portions of
said surface being placed between said portions of filling
material, is/are substantially planar, such as planar, such as
having a radius of curvature being larger, such as 2, 3, 4, 5, 10,
20, 50, 100 times larger, than a distance between neighbouring
portions of filling material, such as an upper edge when observed
in a cross-section being orthogonal to a length direction of said
substrate having a radius of curvature being larger, such as 2, 3,
4, 5, 10, 20, 50, 100 times larger, than a distance between
neighbouring portions of filling material. A possible advantage of
having said one or more portions of said surface being placed
between said portions of filling material substantially planar,
such as planar, may be, that it facilitates providing said portions
of said surface with a low surface roughness, which may in turn be
beneficial for the electrical properties of a subsequently
deposited superconducting layer.
[0126] In an embodiment, there is provided a substrate suitable for
supporting an elongated superconducting element, comprising a
plurality of portions of filling material, such as at least 3
portions of filling material, being substantially parallel, such as
parallel with each other, and wherein a surface of the solid
element, such as an upper surface, upon which the filling material
is placed, is substantially planar, such as planar, such as having
a radius of curvature being larger, such as 2, 3, 4, 5, 10, 20, 50,
100 times larger, than a distance between neighbouring portions of
filling material, such as an upper edge when observed in a
cross-section being orthogonal to a length direction of said
substrate having a radius of curvature being larger, such as 2, 3,
4, 5, 10, 20, 50, 100 times larger, than a distance between
neighbouring portions of filling material. A possible advantage of
having said surface being substantially planar, such as planar, may
be, that it facilitates in a simple way providing portions of said
surface being placed between or adjacent one or more portions of
filling material which are planar, which in turn facilitates
providing said portions of said surface with a low surface
roughness, which may in turn be beneficial for the electrical
properties of a subsequently deposited superconducting layer. The
surface of the solid element may have portions (or areas) below and
between portions of filling material, which portions or areas are
flush with each other. By `flush` may be understood that the
different portions or areas of the surface together form a surface
without bends, breaks, or irregularities, such as a substantially
planar surface, such as a planar surface.
[0127] In an embodiment, there is provided a substrate suitable for
supporting an elongated superconducting element, comprising a
plurality of portions of filling material, such as at least 3
portions of filling material, wherein the substrate is a tape,
wherein the length of the substrate is at least 1 m, wherein the
filling material is a homogeneous material, and wherein said
substrate is comprising a plurality of portions of filling material
being substantially parallel, and wherein one or more portions of a
surface of the solid element, upon which the filling material is
placed, said one or more portions of said surface being placed
between said portions of filling material, is/are substantially
planar.
[0128] According to a fourth aspect of the invention, there is
provided an elongated superconducting element comprising: [0129] A
substrate according to the third aspect of the invention, [0130] a
superconducting layer placed, on the substrate or on a buffer on
[0131] the substrate, so that the undercut volumes (332) physically
separates individual lines of superconducting material or so that
the undercut volumes (332) serve to physically separate individual
lines of superconducting material and/or buffer material.
[0132] According to a fifth aspect of the invention, there is
provided an apparatus for carrying out the method according to the
third and/or fourth aspect of the invention.
[0133] According to a sixth aspect of the invention, there is
provided use of an elongated superconducting element according to
the fourth aspect of the invention and/or an elongated
superconducting element (601) produced according to the second
aspect, within any one of a performance magnetic coil, a
transformer, a generator, a motor, an electro-motor, a magnetic
resonance scanner, a cryostat magnet, a large hadron collider, an
AC power grid cable, a DC power grid cable, a smart grid,
tokamak.
[0134] The first, second, third, fourth, fifth, and sixth aspect of
the present invention may each be combined with any of the other
aspects. These and other aspects of the invention will be apparent
from and elucidated with reference to the embodiments described
hereinafter.
BRIEF DESCRIPTION OF THE FIGURES
[0135] The first, second, third, fourth, fifth and sixth aspects
according to the invention will now be described in more detail
with regard to the accompanying figures. The figures show one way
of implementing the present invention and is not to be construed as
being limiting to other possible embodiments falling within the
scope of the attached claim set.
[0136] FIG. 1 shows a typical superconductor structure,
[0137] FIG. 2 illustrates a non-striated (a) and a striated (b)
superconductor,
[0138] FIG. 3 shows steps of a fabrication process,
[0139] FIGS. 4-5 shows steps in an alternative fabrication
process,
[0140] FIG. 6 shows steps of a fabrication process,
[0141] FIG. 7 illustrates dimensions of disruptive strips,
[0142] FIG. 8 illustrates dimensions of a superconducting
structure,
[0143] FIGS. 9-10 are top views showing portions of filling
material shadowing undercuts,
[0144] FIGS. 11-12 are cross-sections of a solid element with
masking- and filling material,
[0145] FIG. 13 corresponds to FIGS. 11-12 after removal of masking
material,
[0146] FIG. 14 is a cross-section of a sample where Ag is deposited
over an undercut,
[0147] FIG. 15 shows an apparatus for carrying out the method
according to the first aspect.
[0148] FIG. 16 illustrates a process flow according to an
embodiment,
[0149] FIG. 17-18 show samples prepared according to
embodiments,
[0150] FIG. 19 illustrates a process flow according to an
embodiment,
[0151] FIG. 20 shows a sample prepared according to an
embodiment,
[0152] FIG. 21 illustrates a process flow according to additional
steps.
DETAILED DESCRIPTION OF AN EMBODIMENT
[0153] FIG. 1 shows a typical superconductor structure, which is a
sandwich structure comprising a substrate 102, a buffer and the
superconducting material 106. In the present figure, the current is
supposed to flow through the superconducting material 106 in the
z-direction.
[0154] When the superconducting material is a relatively wide
(where width is measured in the x-direction) layer of material,
such as when formed as a layer on a wide planar substrate, the
superconducting layer exhibits relatively large AC losses which
could be reduced by turning the single, wide superconducting layer
into a plurality of relatively narrow lines (i.e., lines with
cross-sections in the yx-plane where the widths measured in the
x-direction are smaller compared to the original, wide layer).
[0155] FIG. 2 is a top view of a superconducting material, where
the left side (a) illustrates a non-striated superconductor 208
formed on a planar layer, and the right side (b) illustrates a
striated superconductor, where individual lines 210 of
superconducting material have been formed are separated from
adjacent lines of superconducting material by non-superconducting
lines 212. It is understood that current runs in a direction
parallel to the lines, and that the width is the dimension of the
lines in a direction orthogonal to the direction of the
current.
[0156] Due to electromagnetic effects, AC losses are present in
superconducting tapes, and this problem scales with the width of
the superconductor. Consequently, it is suggested to overcome this
problem by replacing the wide superconductor layer (corresponding
to the superconductor layer in FIG. 2(b)) by a plurality of thin
superconductor lines (corresponding to the separated, adjacent
lines in FIG. 2(a)).
[0157] FIG. 3 shows steps of a fabrication process, and thus
illustrates a method for producing a substrate suitable for
supporting an elongated superconducting element, such as a
superconducting tape having reduced AC losses.
[0158] FIG. 3A shows a perspective view of a solid element 202, the
solid element 202 having an upper surface 314 being substantially
uniform.
[0159] Generally, the solid element material (tape/wire/cylinder)
in an as-rolled (or as-prepared) condition and e.g. with a
thickness close to the final thickness may be fully or partially
annealed during a heat treatment in a protective atmosphere or
air.
[0160] FIG. 3B shows a side view of the solid element where the
side of the solid element 202 can be seen. The thickness 353
(extension along a first dimension, which is in the y-axis) of the
solid element 202 may be significantly smaller, such as 10, 100 or
1000 times smaller, than its width (extension along a second
dimension, which is parallel to the x-axis) and where the width is
significantly smaller, such as 10, 100, or 1000 times smaller, than
length (extension along a third dimension, which is parallel to the
z-axis). The thickness 353 may in exemplary embodiments be 10
micrometer, such as 20, such as 50 micrometer, such as 100
micrometer, such as 1 mm, such as within 10 micrometer-1 mm.
[0161] FIG. 3C shows the solid element 202 after a step of placing
a plurality of elongated strips of masking material 316a, 316b on
the solid element, where the elongated strips of masking material
are arranged so as to form three exposed elongated areas 323a-c,
where each exposed elongated area is delimited on one or two sides
by at least one elongated strip of masking material. For example,
the exposed elongated area 323a which is placed to the left is
delimited on only one side by an elongated strip 316a of masking
material and on the other side by an edge of the solid element 202.
The exposed elongated area 323b which is placed in the middle is
delimited on two sides by adjacent elongated strips 316a-b of
masking material.
[0162] FIG. 3D-E shows placing filling material 317 on the solid
element 202, more particularly on the surface 314 of the solid
element. It may be understood that the filling material may be or
is placed so as to form a homogeneous filling material.
[0163] FIG. 3E shows the situation after the step of placing
filling material 317 on the solid element 202, more particularly on
the surface 314 of the solid element, so that each exposed
elongated area 323a-c is covered by a coherent portion of filling
material, where each portion of filling material 318a-c also covers
at least a portion of the adjacent elongated strip(s) of masking
material. It may be understood that the filling material 318a-c may
be homogeneous or is homogeneous. It appears from the figures, that
the masking strips 316a-b have a trapezoidal shape which may aid in
achieving that each portion of filling material also covers at
least a portion of the adjacent elongated strip(s) of masking
material. However, it is also encompassed that masking strips have
other shapes, such as triangular, rectangular or circular.
[0164] FIG. 3F shows the situation where a substrate 300 suitable
for supporting an elongated superconducting element has been
provided after a step of removing the elongated strips of masking
material 316a-b so as to form corresponding undercut volumes 332,
where each undercut volume within the one or more undercut volumes
is formed along a portion of filling material and between the
portion of filling material and the solid element. The volumes 328
between the portions of filling material may be referred to as
`disruptive strips` 328. The undercut volumes 332 are positioned
between the portions of filling material 318a-c and the solid
element 202, such as the undercuts being regions which are above
the surface of the solid element, but which are also shadowed when
observed from above.
[0165] The resulting surface profile, cross-sectional profile and
surface texture may be inspected using a means for measuring
microtexture, such as a scanning electron microscope (SEM) equipped
with an Electron Backscatter Diffraction Detector (EBSD) detector
and which may in a particular embodiment employ software for
measuring and analysing texture, such as HKL Technology-Channel 5
software. Note that texture measurements may only be necessary for
textured substrate materials.
[0166] FIGS. 4-5 shows steps in an alternative fabrication
process.
[0167] FIG. 4 shows a situation similar to FIG. 3E, except that the
elongated strips of masking material 416a-b each have a rectangular
(and not trapezoidal) cross-section, and furthermore, that the
portions of filling material 418a-c extends above the masking
material in the upwards y-direction, and partially over the masking
material in the x-direction.
[0168] FIG. 5 shows a situation corresponding to FIG. 4 although
the masking material has been removed (similar to FIG. 3F vs. FIG.
3E), i.e., a situation where a substrate 400 suitable for
supporting an elongated superconducting element has been provided
after a step of removing the elongated strips of masking material
416a-b so as to form corresponding undercut volumes 432. The
volumes 428 between the portions of filling material may be
referred to as `disruptive strips` 428. Thus, even though the sides
of the elongated strips of masking material are vertical, it may
still be possible to realize the undercuts 432. In an embodiment,
the elongated strips of masking material are striated Kapton.RTM.
tape, where Cu has been placed on portions adjacent the edges of
each strip of tape, which facilitates the embodiment in FIGS. 4-5,
e.g., by means of electrodeposition of filling material.
[0169] In each of FIG. 3F and FIG. 5, there is provided a substrate
suitable for supporting an elongated superconducting element,
comprising a plurality of portions of filling material
(corresponding, respectively, to filling material 318a-c and
filling material 418a-c) being substantially parallel, such as
parallel with each other, and wherein a surface (surface 314 in
FIG. 3B) of the solid element (202), such as an upper surface, upon
which the filling material is placed, is substantially planar, such
as planar, such as having a radius of curvature being larger than a
distance (corresponding to distance 750 in FIG. 7) between
neighbouring portions of filling material. The planarity may be
seen as said surface of said solid forming a straight line when
observed in a cross-section (as in each of FIG. 3F and FIG. 5)
being orthogonal to a length direction (corresponding to the
z-direction in each of FIG. 3F and FIG. 5) of said substrate, such
as said straight line having a radius of curvature being larger,
such as 2, 3, 4, 5, 10, 20, 50, 100 times larger, than a distance
between neighbouring portions of filling material
[0170] FIG. 6 shows steps of a fabrication process for producing an
elongated superconducting element.
[0171] FIG. 6A shows a situation similar to the situation of FIG.
3F, i.e., a substrate 300 suitable for supporting an elongated
superconducting element, where undercut volumes 332 are formed
between the surface of the solid element 202 and the portions of
filling material, such as indicated by the dotted lines 336,
338.
[0172] FIG. 6B shows placing, such as depositing, a layer of buffer
material 640 on the substrate suitable for supporting an elongated
superconducting element, more specifically one the portions of
filling material and on the bottom of volumes bounded on three
sides by the solid element and by adjacent portions of filling
material, thereby forming an exemplary a substrate 600 suitable for
supporting an elongated superconducting element, which substrate
comprises a buffer layer 640. It is noted that undercuts 632 may
still be present even after placement of the buffer layer.
[0173] A ceramic buffer layer stack (e.g.
Y.sub.2O.sub.3/YSZ/CeO.sub.2 for textured substrates) and
superconducting layer (such as YBa.sub.2Cu.sub.3O.sub.7) may be
placed, such as deposited, such as deposited by pulsed laser
deposition (PLD) using standard settings, on substrate 300 suitable
for supporting an elongated superconducting element.
[0174] FIG. 6C shows placing a layer of superconducting material
642, 644, 646 on the buffer material, so that the undercut volumes
serve to physically separate individual lines of superconducting
material. It is understood that the distance 648 between a bottom
of the disruptive strips (incl. buffer layer) and the upper surface
of the portions of filling material (incl. buffer layer) is large
enough so as to ensure that the separate portions 642, 644, 646 of
layer of superconducting material on the buffer material is
physically separated.
[0175] The deposition of ceramic buffer layers and superconducting
layer (where at least one layer is deposited by a physical vapour
technique/directional deposition) will only deposit material on the
horizontal surfaces of the substrate. A complete strip decoupling
is achieved via the undercut portions, and furthermore material
usage is minimized. Additional layers (silver/copper) added on top
of the superconductor layer will also be decoupled.
[0176] The performance of the superconducting material with respect
to critical current density (J.sub.c), critical current (I.sub.c),
AC-losses (W) and frequency dependency (f.sub.d) may be measured by
vibrating sample measurements, AC loss measurements (calorimetric
or phase-shift measurements), and transport measurements on small
model samples (5.times.5 mm.sup.2) and 15 cm long samples at
various applied magnetic fields and temperatures. A full scale
superconductor tape, such as one or more meters of superconductor
tape, may be wound into a coil and tested at 77 K applying various
magnetic fields and transport currents. The performance of the
superconducting material may furthermore be quantified via
Hall-probe measurements enabling determining magnetization within
the striated superconductor elements.
[0177] It is noted, that a possible advantage of embodiments of the
invention may be, that a larger critical current (I.sub.c) may be
supported for a structure having a certain width. An explanation of
this is that the total width (extension along the x-axis) of the
separate portions 642, 644, 646 of layer of superconducting
material is relatively large compared to prior art solutions where
material between lines of superconducting material is made
non-superconducting, cf., the embodiment shown in FIG. 2, where the
total width of the striated superconductor (in FIG. 2(b)) is
approximately half the width of the non-striated superconductor (in
FIG. 2(a)). In comparison, with embodiments of the present
invention, the total width of the striated superconductor may be
more than 0.5, 0.6, 0.7, 0.8, 0.9 or 0.95 or 0.99 times the width
of the non-striated superconductor, since the superconducting
material may be placed both between and within disruptive
strips.
[0178] FIG. 7 illustrates dimensions of the disruptive strips 328.
The figure shows a situation similar to FIG. 3F or FIG. 6A.
Furthermore is indicated a distance 748 between a plane being
tangential to upper surfaces of the one or more portions of filling
material and a plane being tangential to bottoms of volumes bounded
on three sides by the solid element and adjacent portions of
filling material. Said distance 748 may preferably be non-zero and
below 4 mm, such as]0; 4[mm, or non-zero and below 1 mm, such as]0;
1[mm. Furthermore is indicated a width 750 of the disruptive strips
(in the filling material) measured in the x-direction, the width
may in exemplary embodiments, be 1 micrometer, such as 2
micrometer, such as 5 micrometer, such as 10 micrometer, such as 30
micrometer, such as 100 micrometer, such as 1 mm, such as within 1
micrometer-1 mm. Furthermore is indicated a distance 752 between
adjacent disruptive strips within the plurality of disruptive
strips which is measured in the x-direction.
[0179] FIG. 8 illustrates dimensions of a superconducting structure
which has thickness 854 (length along a first dimension, which is
in the y-axis) which is significantly smaller, such as 10, 100 or
1000 times smaller, than its width 856 (length along a second
dimension, which is parallel to the x-axis) and where the width 856
is significantly smaller, such as 10, 100, or 1000 times smaller,
than (length along a third dimension, which is parallel to the
z-axis). The figure furthermore shows three layers, such as lines
842, 844, 846, of superconducting material on top of the substrate.
The thickness 854 may in exemplary embodiments be 10 micrometer,
such as 20 micrometer, such as 50 micrometer, such as 100
micrometer, such as 1 mm, such as within 10 micrometer-1 mm. The
width 856 may in exemplary embodiments may in particular
embodiments be 1 micrometer, such as 10 micrometer, such as 100
micrometer, such as 1 mm, such as 10 mm, such as 100 mm, such as 1
m, such as within 1 micrometer-1 m. The length 858 may in
particular embodiments be 1 m, such as 100 m, such as 1 km, such as
20 km, such as 100 km, such as above 100 km, such as within 1 m-30
km, such as within 1 km-30 km. The superconducting structure may be
based on a solid element 803 in the shape of a tape. The length may
be at least 1 m, such as at least 10 m, such as at least 100 m,
such as at least 1 km, such as at least 10 km, such as at least 100
km, such as at least 100 km. It may be understood, that the lengths
of one or more or all of the elements optionally placed on the
substrate, such as elongated strips of masking material, filling
material, buffer, superconducting material, shunt layer may have a
length being similar to or identical to the length of the
substrate.
EXAMPLES
Example A
[0180] In an exemplary embodiment according to the invention, there
may be provided a substrate suitable for supporting an elongated
superconducting element according to the following protocol, which
protocol describes copper plating strips with a shadow-profile on
Hastelloy C276 metal tapes. [0181] 1) The solid element is provided
in form of a metal tape (Hastelloy C276) which is cleaned applying
an alkaline soak, or alternatively, 5 min cleaning in acetone with
ultrasound and then 5 min in ethanol with ultrasound. [0182] 2)
Placing one or more strips of masking material is carried out with
Kapton.RTM. masking tape which is applied in parallel strips on the
up side of the metal tape and smoothened so that there are no air
bubbles between the Kapton.RTM. tape and the metal tape. The edges
of the Kapton.RTM. tape are cut so that the down side of the tape
(glue side) is wider than the up side and preferably so that one or
both edges make an angle of about 45.degree. with the tape plane
(e.g., such as depicted in FIG. 3C). [0183] 3) The down side of the
metal tape is covered completely (non-filamented) with Kapton.RTM.
tape and smoothened to avoid air bubbles. [0184] 4) Acid dip in HCl
(20%) for 5 sec. [0185] 5) Anodic etch ("+" on metal tape) in
Wood's nickel strike solution (solution example: 5 g NiCl.sub.2, 10
ml HCl (37%), 100 ml H.sub.2O), 53 mA/cm.sup.2 for 20-30 sec at
38.degree. C. Do not take the sample out of the solution. [0186] 6)
Placing filling material on the solid element is carried out by
nickel plating (cathodic, i.e. "-" on metal tape) using Wood's
nickel strike solution, 53 mA/cm.sup.2 for 2-3 min. [0187] 7) Rinse
with water and proceed immediately to the copper plating procedure.
[0188] 8) Copper plating in cathodic ("-" on metal tape) setup.
Solution example 24 g CuSO.sub.4, 6 g H.sub.2SO.sub.4, HCl 25 .mu.l
and 100 ml ion-free water. Operation temperature=20.degree. C. and
current density=83 mA/cm.sup.2 for 3-15 min (it may be noted that
the present steps 7-8 may be seen as optional, since it may be
possible to exclusively rely on electrodeposition of nickel, and
thereby render the copper electrodeposition superfluous). [0189] 9)
Rinse the coated tape with water. [0190] 10) Removing the strips of
masking material is carried out by immersing the coated tape in
acetone with ultrasound for about 5 min and then 5 min in ethanol
with ultrasound. The Kapton.RTM. tape can then easily be peeled of
using a tweezer. Rinse again using acetone and ethanol for a few
minutes. [0191] 11) Dry the tape using flowing nitrogen.
Results
[0192] FIG. 9 shows the resulting portions 918 of filling material
which shadows undercuts below a sub-portion of the portions of
filling material as observed with optical microscopy. The
disruptive strips 928 are also indicated. The scale bar is 1 mm, so
the widths of the portions 918 of filling material are
approximately 0.4 mm, and the widths of the disruptive strips 928
are approximately 0.4 mm.
[0193] FIG. 10 is similar to FIG. 9 albeit at a larger
magnification.
[0194] FIGS. 11-13 are cross-sectional views of a sample prepared
according to the protocol of Example A, but with a tape which cut
with a 90.degree. angle and not cut with a 45.degree. angle as
suggested as preferable stated in example A. step 2.
[0195] FIG. 11 is a cross-section of a solid element with masking-
and filling material. The image thus corresponds to FIG. 3E or FIG.
4. More particularly, FIG. 11 is an optical image of the
cross-section of a selectively copper-plated Hastelloy C276 tape
where the protective Kapton.RTM. tape is not removed. The figure
shows a solid element 1102 (being the Hastellogy C276 tape) after a
step of placing a plurality of elongated strips of masking material
1116a, 1116b on the solid element (the masking material being
elongated strips of Kapton.RTM. tape), where the elongated strips
of masking material are arranged so as to form an exposed elongated
area between the elongated strips of masking tape 1116a-b, where
the exposed elongated area is delimited on two sides by adjacent
elongated strips 1116a-b of masking material. Furthermore, the
figure shows that a portion filling material 1118b has been placed
on the solid element 1102, more particularly on the surface of the
solid element corresponding to the exposed elongated area, where
the filling material is electrodeposited copper, so that the
exposed elongated area is covered by a coherent portion of filling
material, where the portion of filling material 1118b also covers
at least a portion of the adjacent elongated strips of masking
material, cf., e.g., the overhanging portions 1119a-b of copper.
Thus, an overhang of electroplated copper is clearly present on top
of the protective Kapton.RTM. tape. The Kapton.RTM. tape is placed
on both sides of the Hastelloy tape to control where electroplated
material is deposited (cf., the elongated masking strips of masking
material 1116a-b on the upper side, and the masking material 1190
on the lower side which is also Kapton.RTM. tape). The scalebar is
100 .mu.m.
[0196] FIG. 12 similar to FIG. 11 albeit at a larger
magnification.
[0197] FIG. 13 corresponds to FIGS. 11-12 after removal of masking
material. The image thus corresponds to FIG. 3F or FIG. 5. More
particularly, the figure shows an optical image of the
cross-section of a selective copper-plated Hastelloy C276 tape
where the protective Kapton.RTM. tape has been removed following
the instructions described in example A. FIG. 13 shows a situation
where the substrate suitable for supporting an elongated
superconducting element has been provided after a step of removing
the elongated strips of masking material so as to form a
corresponding undercut volume 1332, where each undercut volume
within the one or more undercut volumes is formed along a portion
of filling material and between the portion of filling material and
the solid element. The undercut volumes 332 are positioned between
the portions of filling material 1118b and the solid element 1102,
such as the undercuts being regions which are above the surface of
the solid element, but which are also shadowed when observed from
above. An undercut volume is clearly seen between the Hastelloy
tape and the electroplated copper. The Hastelloy tape is
approximately 100 .mu.m thick and the undercut volume extends about
50 .mu.m from the bulk part of the electroplated copper. The
scalebar is 100 .mu.m.
[0198] An apparatus for carrying out the method according to the
first aspect, more specifically for carrying out the process
described in Example A above:
[0199] FIG. 15 shows an apparatus for, such as arranged for,
carrying out the method according to the first aspect, such as an
apparatus arranged for carrying out the protocol as described above
in connection with Example A. The figure shows a reel-to-reel
system, where a metal tape is transferred from a first reel 2271 to
a second reel 2287, and in the process is transformed into a
substrate suitable for supporting an elongated superconducting
element by going through an ultrasound cleaning bath 2272
comprising acetone and/or ethanol (this bath step may be replaced
by or be supplemented with an alkaline soak cleaner), a dryer 2273
using air or nitrogen (N.sub.2), a set of reels comprising an upper
reel 2216 and a lower reel 2218. The upper reel comprises
filamented masking tape, i.e., the tape material is capable of
acting as masking material, which tape has been sectioned into
elongated strips of masking material, which elongated strips of
masking material are transferred from the reel 2216 to an upper
side of the tape so as to place elongated strips of masking
material and thereby form exposed elongated areas (corresponding to
step 2 of the protocol in Example A). The lower reel 2218 comprises
masking tape which is not filamented so that the masking tape may
completely cover a lower side of the metal tape (corresponding to
step 3 of the protocol in Example A), where a possible advantage of
this may be, that during subsequent placement of filling material
on non-masked areas, no filling material is placed on the backside,
where it would serve no purpose). Note that the metal tape
continues as indicated by the dashed line and the metal tape then
proceeds through an acid dip bath 2277 with (HCl) (corresponding to
step 4 of the protocol in Example A), an anodic etch and nickel
plating bath 2278 with Woods nickel strike solution (corresponding
to steps 5-6 of the protocol in Example A), a cleaning bath 2279
with water (corresponding to step 7 of the protocol in Example A),
a copper plating bath 2280 with a solution as described in step 8
of the protocol in Example A--where it may be noted that the steps
7-8 in the protocol in Example A may be seen as optional and that
consequently cleaning bath 2279 and copper plating bath 2280 are
also optional (note that the tape continues as indicated by the
dashed line), a cleaning bath 2281 with water (corresponding to
step 9 of the protocol in Example A), an ultrasound cleaning bath
2282 comprising acetone and an ultrasound cleaning bath 2283
comprising ethanol (corresponding to step 10 of the protocol in
Example A), a dryer 2286 using air or nitrogen (N.sub.2)
(corresponding to step 11 of the protocol in Example A), and
finally the second reel 2287.
Example B
[0200] A layer of masking material is provided by a protective
layer, such as a standard imprint resist or photoresist for UV
lithography, a Kapton.RTM. film or scotch tape.
[0201] The layer of masking material of e.g. photoresist (produced
e.g. using die slot coating or dip coating) or Kapton.RTM. film, or
imprint resist or scotch tape is applied to the sample surface
(i.e., to the surface of the solid element). Forming elongated
strips of masking material is carried out by cutting or
roll-cutting lines into the layer of masking material and
subsequently removing, e.g., every second of the thin strips of
layer of masking material so that the surface of the solid element
is (partially) covered by parallel but separated, elongated strips
of masking material, e.g. strips of Kapton.RTM. film.
Example C
[0202] The starting material, such as the solid element (e.g. a
Hastelloy tape), is coated with elgonated strips of masking
material, such as with Kapton.RTM. film (or wax or lacquer) in
stripes parallel to the length of the metal tape. The stripes
should be e.g. 1 mm wide and positioned with a spacing of, e.g., 1
mm. Notice that the Kapton.RTM. film may be firmly attached to the
sample, e.g. using a brush or rubber rolls. Masking material, such
as protective lacquer or wax, may be coated in parallel lines using
a slot die coater or an alternative standard coating process. This
lacquer or wax can subsequently be removed using e.g. acetone or
hot water.
Example D
[0203] FIG. 14 shows an optical microscopy image of a cross-section
of a sample where an elongated cavity has been formed in a lower
layer 1403 and where an upper layer 1424 extends approximately 5
.mu.m from the "bulk" and thus overhangs the cavity with
approximately 5 micrometer.
[0204] Furthermore, a 500 nm silver layer 1464, 1466 was deposited
on the sample which was positioned horizontally above the silver
source, i.e. the normal of the sample surface was parallel to the
line-of-sight direction from the silver source. The sample was
mounted either using adhesive carbon pads or a small metal holder.
The sample was coated with a silver layer using physical vapour
deposition (E-beam evaporation, Alcatel machine). A 500 nm thick
silver layer was produced at a deposition rate of .about.7 .ANG./s
and a pressure of .about.6.times.10.sup.-6 mbar.
[0205] The figure shows that the silver layer is physically
separated as indicated in the gap 1465 at the left side of the
profile due to the undercut feature between the lower layer 1403,
being a Hastelloy metal tape and the upper layer 1424, being an
oxide/nitride surface coating. Importantly, about 5 .mu.m of the
undercut feature (which in the present figure is given by the
overhanging remaining portion of the upper layer 1424) is
sufficient to produce a significant separation of the silver layer
1464 on top of the upper layer 1424 and the silver layer 1466 at
the bottom of the etched volume.
[0206] In the following, there is described embodiments of methods
for producing a substrate suitable for supporting an elongated
superconducting element. Note that the methods 1-4 described below
specifies methods for making substrates, such as filament
structures, with filling material and undercuts on only one side
(which may be referred to as the upper side) of the substrate/metal
tape/solid element and that the methods may in alternative
embodiments encompassed by the present invention be applied on both
sides simultaneously or sequentially, so as to enable producing
substrates suitable for supporting an elongated superconducting
element, where said substrates have one or more portions of filling
material with corresponding undercut volumes on both an upper and a
lower side.
METHOD-1: "Masking Tape and Electroplating Using Two Different
Ni-Types"
METHOD-1A:
[0207] FIG. 16 illustrates the process flow for METHOD-1A, with
sub-figures (a)-(h) corresponding to method steps 1-8 described
below.
STEP 1 corresponding to FIG. 16(a): The raw substrate (which may be
referred to as solid element) is cleaned using a standard degreaser
[1]. STEP 2 corresponding to FIG. 16(b): A masking tape, such as
adhesive Kapton tape, is applied to the bottom side of the
substrate. STEP 3 corresponding to FIG. 16(c): A standard Woods
nickel strike [1] is electroplated on to the upper side of the
substrate (this step is typically seen as advantageous for
stainless steel and stainless alloy materials). STEP 4
corresponding to FIG. 16(d): A standard bright nickel layer [1] is
electroplated on to the Woods nickel strike layer (this standard
bright nickel layer has a smoother surface which ensures a low
surface roughness that is beneficial for further buffer layer
growth and eventually the superconducting layer). STEP 5
corresponding to FIG. 16(e): A masking material in the form of a
masking tape, such as adhesive Kapton tape, is applied to the upper
side of the substrate. STEP 6 corresponding to FIG. 16(f): The
masking tape is mechanically cut, e.g. with an angle, using knifes
and the tape portions with an inverted trapeze (i.e., the portions
which in the cross-section in FIG. 16(f) would have had an
increasing with in a direction away from the solid element) is
removed by peeling off the tape-parts. FIG. 16(f) illustrates the
situation after said removal. Alternatively, the tape is cut before
it is applied on to the bright nickel layer, and the portion which
are shown in FIG. 16(f) are placed on the substrate. The remaining
portions of tape correspond to elongated strips of masking material
on the solid element. STEP 7 corresponding to FIG. 16(g): An
additional bright nickel layer is plated on to the areas not
covered by the masking tape and this layer will fill up the
portions adjacent to and between the masking material (remaining
Kapton tape). This additional bright nickel layer corresponds to
filling material. STEP 8 corresponding to FIG. 16(h): The masking
tape is peeled off (e.g. while applying heat to soften the masking
tape), or dissolved using an appropriate solvent such as acetone,
leaving only the metal structure on the surface, i.e, removing the
one or more elongated strips of masking material so as to form one
or more corresponding undercut volumes, where each undercut volume
within the one or more undercut volumes is formed along a portion
of filling material and between the portion of filling material and
the solid element.
METHOD-1B:
[0208] FIG. 17 shows a sample prepared following the processing
steps described below.
[0209] The Hastelloy C276 metal tape 1702 (corresponding to a solid
element) was degreased using an ultrasonic bath containing first
acetone and then ethanol for 1 min each, respectively. The metal
tape 1702 was then covered with masking tape (Kapton tape) on the
lower side (see lower side masking tape 1716b in the bottom of FIG.
17) and on the upper side. The upper side Kapton tape was then cut
using a 45.degree. tilted knife in a reel-to-reel system and the
Kapton tape strip with the inverted trapeze shape was peeled off
leaving only the trapeze shaped portions 1716a (corresponding to
the masking material as shown in FIG. 3C and FIG. 16(f)). The
sample was emerged into a standard Woods nickel strike solution
[1], which was heated to 32.degree. C. The sample was then etched
(anodic current) applying 16 mA/cm.sup.2 for about 1 min with
magnetic stirring (220 RPM). A nickel layer (Woods Ni layer 1718
corresponding to a homogeneous filling material) was then
electroplated (cathodic current) onto the areas not covered by the
masking tape 1716a-b using the standard Woods nickel solution that
was still heated to 32.degree. C. A pure nickel electrode (99.99%),
220 RPM magnetic stirring and a current density equal to 54
mA/cm.sup.2 was applied for 12 min.
[0210] A thinner smooth bright nickel surface layer (bright Ni
layer 1717) was electroplated, on top of the Woods nickel layer. A
standard bright nickel solution, SurTec 856 [2] from SurTec
Scandinavia ApS, was used and it was heated to 42.degree. C.,
circulated using a pump system (flow in the range of 1-10 L/min)
and electroplating was performed by applying 54 mA/cm.sup.2 for
about 1 min using a pure nickel electrode. The sample was following
cleaned several times in deionized water, ethanol and finally dried
using flowing N.sub.2. Notice that in FIG. 17 the masking tape
trapeze 1716a has not been removed.
[0211] The figure shows that an undercut volume 1732 is present
between the homogeneous filling material 1718 and the solid element
1702.
METHOD-1C:
[0212] FIG. 18 shows a sample with a metal tape 1802 and filling
material 1818 prepared using the parameters described above in
connection with the sample shown in FIG. 17, except that for the
sample shown in FIG. 18 the masking tape has been completely
removed and the substrate has subsequently to said removal been
further coated with SiO.sub.2 1863 and subsequently Ag 1864 using a
standard sputtering process. The figure shows, that the undercut
volume 1832 causes a physical separation of the Ag layer on each
side of the undercut volume.
METHOD-2
"Masking Tape and Electroplating Using Two Different Metals and Two
Different Ni-Types"
METHOD-2A:
[0213] FIG. 19 illustrates the process flow for METHOD-2, with
sub-figures (a)-(i) corresponding to method steps 1-9 described
below.
STEP 1 corresponding to FIG. 19(a): The raw substrate (which may be
referred to as solid element) is cleaned using a standard degreaser
[1]. STEP 2 corresponding to FIG. 19(b): A masking tape such as
adhesive Kapton tape is applied to the bottom side of the
substrate. STEP 3 corresponding to FIG. 19(c): A standard Woods
nickel strike [1] is electroplated on to the upper side of the
substrate (this step is typically seen as advantageous for
stainless steel and stainless alloy materials). STEP 4
corresponding to FIG. 19(d): A standard bright nickel layer [1] is
electroplated plated on to the Woods nickel strike layer (this
standard bright nickel layer has a smoother surface which ensures a
low surface roughness that is beneficial for further buffer layer
growth). STEP 5 corresponding to FIG. 19(e): A masking tape, such
as adhesive Kapton tape, is applied to the upper side of the
substrate. STEP 6 corresponding to FIG. 19(f): The masking tape is
mechanically cut, e.g. with an angle, using knifes and the tape
portions with an inverted trapeze (i.e., the portions which in the
cross-section in FIG. 16(f) would have had an increasing with in a
direction away from the solid element) is removed by peeling off
the tape-parts. FIG. 16(f) illustrates the situation after said
removal. Alternatively, the tape is cut before it is applied on to
the bright nickel layer, and the portion which are shown in FIG.
16(f) are placed on the substrate. The remaining portions of tape
correspond to elongated strips of masking material on the solid
element. STEP 7 corresponding to FIG. 19(g): A copper layer is
electroplated onto the areas not covered by the masking tape using
a standard sulfate-based Cu-plating solution [1]. STEP 8
corresponding to FIG. 19(h): A bright nickel layer is electroplated
onto the areas not covered by the masking tape and it fills ("grows
up against") the portions not covered by the filling material
(Kapton tape). STEP 9 corresponding to FIG. 19(i): The masking tape
is peeled off (e.g. while applying heat to soften the masking
tape), or dissolved using an appropriate solvent such as acetone,
leaving only the metal structure on the surface.
[0214] METHOD-2 differs from METHOD-1 in that the filling material
is provided in a two-step process, which is reflected in STEP 6 and
STEP 7 of METHOD-2A (and corresponding to FIGS. 19(g)-(h)). An
advantage of such two-step process may be, that a core of a
non-magnetic material (e.g., Cu) can be applied, and then a
magnetic material may be applied thereto (e.g., Ni). An advantage
of this may in turn enable benefiting from the good chemical
properties of Ni (resistance towards oxidation) and the good
magnetic properties of Cu (non-magnetic, which may enable reducing
losses due to hysterisis).
METHOD-2B:
[0215] FIG. 20 shows a sample prepared following processing steps
described below.
[0216] The Hastelloy C276 metal tape 2002a was degreased using an
ultrasonic bath containing first acetone and then ethanol for 1 min
each, respectively. The metal tape was then covered with masking
Kapton tape on the lower side. The sample was then emerged into a
standard Woods nickel strike solution [1], which was heated to
32.degree. C. and then the sample was etched (anodic current)
applying 16 mA/cm.sup.2 for about 1 min with magnetic stirring (220
RPM). A nickel layer 2002b was then electroplated (cathodic
current) onto the upper metal tape surface (which was at this point
not covered by the masking tape) using the standard Woods nickel
solution that was still heated to 32.degree. C., a pure nickel
electrode (99.99%), 220 RPM magnetic stirring and applying 54
mA/cm.sup.2 for about 12 min. It is noted, that in this example,
the tape 2002a and the nickel layer 200b may together be seen as a
solid element.
[0217] The upper part of the metal tape 2002a with nickel layer
2002b was then covered with masking Kapton tape which was
subsequently cut using a 45.degree. tilted knife in a reel-to-reel
system and the Kapton tape strip with the reversed trapeze shape
was peeled off leaving only the trapeze shaped areas (corresponding
to the masking material as shown in FIG. 3C and FIG. 19(f)).
[0218] A copper layer 2018 was electroplated onto the areas not
covered by the masking tape using a standard sulfate-based copper
bath solution [1] used at room temperature .about.25.degree. C.,
electrodes were phosphorized (0.02-0.08% by weight phosphorus),
oxide-free, high-purity copper nuggets on a Ti-rod placed in a
standard anode bag, 220 RPM magnetic stirring and applying 30
mA/cm.sup.2 for about 10 min.
[0219] A thinner smooth bright nickel surface layer 2017 was
electroplated, on top of the copper layer 2018 using a standard
bright nickel solution, SurTec 856 [2] from SurTec Scandinavia ApS,
which was heated to 42.degree. C., circulated using a pump system
(flow in the range of 1-10 L/min) and electroplating was performed
by applying 54 mA/cm.sup.2 for about 1 min. The sample was
following cleaned several times in deionized water, ethanol and
finally dried using flowing N.sub.2. The copper layer 2018 may be
seen as a homogeneous filling material. Alternatively, The copper
layer 2018 and bright nickel surface layer 2017 may be seen as
filling material.
METHOD-3
"Filling Material Portions Made in Buffer Layer Using Chemical
Solution Deposition"
[0220] STEP1: The raw substrate, such as Hastelloy C276 or Ni--W,
is cleaned using a standard degreaser [1]. STEP2: A masking tape,
such as adhesive Kapton tape is applied to the bottom side of the
substrate. STEP3: One or more buffer layer(s), such as
Y.sub.2O.sub.3, Al.sub.2O.sub.3, Yttrium Stabilized Zirconium,
CeO.sub.2, MgO, Gd.sub.2Zr.sub.2O.sub.7 is coated onto the upper
side of the substrate using chemical solution deposition and
coating by e.g. dip-coating or ink-jet printing, and may be
alternatively be carried out before STEP2. The present step ensures
a smooth surface and particularly if using the solution deposition
planarization technique [3]. Additionally, if the metal substrate
material is textured this may transfer the texture to the buffer
layer (however, typically not for the solution deposition
planarization). These layers are dried at an elevated temperature
around e.g. 200.degree. C., while final sintering at a higher
temperature may be performed after the masking material has been
removed. This buffer-covered substrate forms the solid element.
STEP4: A pre-cut (e.g. mechanically cut using 45.degree. tilted
knifes) adhesive Kapton tape is applied onto the dried buffer
layers so as to form elongated strips of masking material,
corresponding to the masking material in, e.g., FIG. 3C. This
masking material may beneficially have a surface property that
enables that subsequently deposited buffer layer material contact
angle on the masking material is high ("hydrophobic") so that it is
not wetting the surface and therefore not covering/sticking to the
masking material but enables subsequently deposited buffer layer
material to be confined in the plane by the masking material
portions. STEP5: One or more additional buffer layer(s) are coated
onto the tape, which additional buffer layers correspond to filling
material, which then fills the portions between the masking
materials and inherits the (inverse of the) shape of the masking
material. STEP6: The masking tape is peeled off (e.g. while
applying heat to soften the masking tape), or dissolved using an
appropriate solvent leaving only the buffer layer profile structure
on the surface. STEP7: The buffer layer material is sintered at an
elevated temperature and further processed in view of coated
conductor fabrication.
[0221] A possible advantage of METHOD-3 may be, that both the
surfaces of the filling material and the surfaces of the solid
element between the portions of filling material may be buffer
material.
METHOD-4
"Masking Material Applied Using Ink-Jet Printing"
[0222] STEP1: The raw substrate, such as Hastelloy C276 or Ni-W, is
cleaned using a standard degreaser [1]. STEP2: A masking tape, such
as adhesive Kapton tape is applied to the bottom side of the
substrate. STEP3: A masking material is applied using ink-jet
printing and produced so that narrow separated lines are formed,
i.e., elongated strips of masking material is formed. The masking
material may be appropriate for e.g. electroplating or chemical
solution deposition of filling material. It is beneficial to
utilize ink-jet printing or alternatively micro/nano-roll
imprinting (imprint lithography) for this process, since the
filament width can be reduced and filaments widths in the
micro/nanometer range may be obtained. STEP4: Either a series of
electroplated layers (see e.g. METHOD-1A, STEPS 3-8) or a buffer
layer filling (see METHOD-3, STEPS 5-7) is applied.
[0223] FIG. 21 illustrates an additional step. To any one of the
last step in any one of the methods, in particular any one of
METHODS-1-4, it may be beneficial to add an additional layer of
e.g. Ni or Cr, which will cover the entire structure (as
illustrated in FIGS. 21(a)-(b)), and have a layer thickness
entailing that will not fill the undercut volume but will insure
that e.g. electroplated copper is protected against oxygenation
during further processing, such as a thickness of e.g. within 100
nm-1 .mu.m.
[0224] REFERENCES for the preceding section describing methods 1-4,
which references are each included by reference in entirety: [0225]
[1] Surface Finishing Guidebook, 79.sup.th edition, 10th Issue by
Metal Finishing Magazine, Fall 2011, VOLUME 109 NUMBER 11A, [0226]
[2] SURTEC 856, Glansnikkel for tromle og stel, [0227] [3] Sheehan
et al., Appl. Phys. Lett. 98, 071907 (2011);
http://dx.doi.org/10.1063/1.3554754
[0228] To sum up, there is provided a method for producing a
substrate (300) suitable for supporting an elongated
superconducting element, wherein one or more elongated strips of
masking material are placed on a solid element (202) so as to form
one or more exposed elongated areas being delimited on one or two
sides by elongated strip of masking material, and placing filling
material on the solid element so that each exposed elongated area
within the one or more exposed elongated areas is covered by a
portion of filling material (318a-c) where each portion of filling
material also covers at least a portion of the adjacent elongated
strip of masking material and subsequently removing the one or more
elongated strips of masking material so as to form one or more
corresponding undercut volumes, where each undercut volume within
the one or more undercut volumes is formed along a portion of
filling material and between the portion of filling material and
the solid element. The method may further comprise placing buffer
material (640) and or superconducting material (642, 644, 646)) on
the substrate, so as to provide a superconducting structure (601)
with reduced AC losses.
[0229] In embodiments E1-E15 of the invention, there is presented:
[0230] E1.A method for producing a substrate (300) suitable for
supporting an elongated superconducting element, the method
comprising: [0231] Providing a solid element (202), [0232] Placing
one or more elongated strips 316a-b of masking material on the
solid element, where the one or more elongated strips of masking
material are arranged so as to form one or more exposed elongated
areas (323a-c), where each exposed elongated area within the one or
more exposed elongated areas is delimited on one or two sides by at
least one elongated strip of masking material within the one more
elongated strips of masking material, [0233] Placing filling
material (317) on the solid element so that each exposed elongated
area within the one or more exposed elongated areas is covered by a
portion of filling material (318a-c), where each portion of filling
material also covers at least a portion of the adjacent elongated
strip of masking material, [0234] Removing the one or more
elongated strips of masking material so as to form one or more
corresponding undercut volumes, where each undercut volume within
the one or more undercut volumes is formed along a portion of
filling material and between the portion of filling material and
the solid element. [0235] E2.A method for producing a substrate
(300) suitable for supporting an elongated superconducting element
according to any of the preceding embodiments, wherein the step of
[0236] Placing one or more elongated strips of masking material on
the solid element, where the one or more elongated strips of
masking material are arranged so as to form one or more exposed
elongated areas, where each exposed elongated area within the one
or more exposed elongated areas is delimited on one or two sides by
at least one elongated strip of masking material within the one
more elongated strip of masking material, [0237] comprises [0238]
Placing a plurality of elongated strips of masking material on the
solid element, where adjacent elongated strips of masking material
within the plurality of elongated strips of masking material are
arranged so as to form a plurality of exposed elongated areas,
where each exposed elongated area within the one or more exposed
elongated areas is formed adjacent to at least one elongated strip
of masking material, and wherein one or more exposed elongated
areas within the plurality of exposed elongated areas is formed
between adjacent elongated strips of masking material. [0239] E3.A
method for producing a substrate (300) suitable for supporting an
elongated superconducting element according to embodiment E2, where
adjacent elongated strips of masking material within the plurality
of elongated strips of masking material are substantially parallel
with each other. [0240] E4.A method for producing a substrate (300)
suitable for supporting an elongated superconducting element
according to any of the preceding embodiments, wherein the solid
element is an ellipsoidal cylinder. [0241] E5.A method for
producing a substrate (300) suitable for supporting an elongated
superconducting element according to any one of embodiments E2-E3,
wherein a distance (752) between adjacent elongated strips of
masking material within the plurality of elongated strips of
masking material is within 1 micrometer-1 millimeter. [0242] E6.A
method for producing a substrate (300) suitable for supporting an
elongated superconducting element according to any of the preceding
embodiments, wherein a distance (748) is given between a plane
being tangential to upper surfaces of the one or more portions of
filling material (318a-c) after the step of [0243] Removing the one
or more elongated strips of masking material so as to form one or
more corresponding undercut volumes, where each undercut volume
within the one or more undercut volumes is formed along a portion
of filling material and between the portion of filling material and
the solid element, [0244] and a plane being tangential to bottoms
of volumes bounded on at least two sides by the solid element and
one or more adjacent portions of filling material, and wherein said
distance (748) is large enough so as to enable that a
superconducting material placed on the substrate may have portions
[0245] on the bottoms of volumes bounded on at least two sides by
the solid element and one or more adjacent portions of filling
material, [0246] and/or [0247] on the one or more portions of
filling material, [0248] which portions of superconducting material
are physically separated. [0249] E7.A method for producing a
substrate (300) suitable for supporting an elongated
superconducting element according to any of the preceding
embodiments, wherein the method further comprises placing a layer
of buffer material (640) on [0250] the one or more portions of
filling material (318a-c) [0251] and/or on [0252] one or more sides
of the volumes bounded on at least two sides by the solid element
and one or more adjacent portions of filling material. [0253] E8.A
method for producing an elongated superconducting element (601),
wherein the method comprises the steps of producing a substrate
suitable for supporting an elongated superconducting element
according to any one of embodiments E1-E7, and wherein the method
further comprises placing a layer of superconducting material (642,
644, 646) [0254] on the one or more portions of filling material
(318a-c) [0255] and/or on [0256] a bottom of volumes bounded on at
least two sides by the solid element and one or more adjacent
portions of filling material, [0257] so that the undercut volumes
(332) serve to physically separate individual lines of
superconducting material. [0258] E9.A method for producing an
elongated superconducting element (601), wherein the method
comprises the steps of producing a substrate suitable for
supporting an elongated superconducting element according to any
one of embodiments E1-E7, and wherein the method further comprises
placing, [0259] c. a layer of buffer material (640) [0260] on the
one or more portions of filling material (318a-c) [0261] and/or
[0262] on bottoms of volumes bounded on at least two sides by the
solid element and one or more adjacent portions of filling
material, [0263] of the substrate suitable for supporting an
elongated superconducting element provided according to any one of
embodiments E1-E7, and [0264] d. a layer of superconducting
material (642, 644, 646) on the buffer material, [0265] so that the
undercut volumes (332) serve to physically separate individual
lines of superconducting material and/or buffer material. [0266]
E10. A method for producing an elongated superconducting element
(601) according to any one of embodiments E8-E9, wherein the step
of placing a layer of superconducting material (642, 644, 646)
and/or a layer of buffer material (640) is a line-of-sight process.
[0267] E11. A substrate (300) suitable for supporting an elongated
superconducting element, the substrate comprising: [0268] A solid
element, [0269] One or more portions of filling material on the
solid element and arranged so that a plurality of undercut volumes
is formed along each portion of filling material and between the
portion of filling material and the solid element. [0270] E12. A
substrate (300) suitable for supporting an elongated
superconducting element according to embodiment E11, wherein the
substrate is a tape. [0271] E13. An elongated superconducting
element (601) comprising: [0272] A substrate according to any one
of embodiments E11-E12, [0273] a superconducting layer placed on
the substrate or on a buffer on the substrate, so that the undercut
volumes (332) physically separates individual lines of
superconducting material or so that the undercut volumes (332)
serve to physically separate individual lines of superconducting
material and/or buffer material. [0274] E14. An apparatus for
carrying out the method according to any one of embodiments E1-E10.
[0275] E15. Use of an elongated superconducting element (601)
according to embodiment E13, within any one of a performance
magnetic coil, a transformer, a generator, a motor, an
electro-motor, a magnetic resonance scanner, a cryostat magnet, a
large hadron collider, an AC power grid cable, a smart grid.
[0276] For the above embodiments E1-E15, it may be understood that
reference to preceding `embodiments` may refer to preceding
embodiments within embodiments E1-E15.
[0277] Although the present invention has been described in
connection with the specified embodiments, it should not be
construed as being in any way limited to the presented examples.
The scope of the present invention is set out by the accompanying
claim set. In the context of the claims, the terms "comprising" or
"comprises" do not exclude other possible elements or steps. Also,
the mentioning of references such as "a" or "an" etc. should not be
construed as excluding a plurality. The use of reference signs in
the claims with respect to elements indicated in the figures shall
also not be construed as limiting the scope of the invention.
Furthermore, individual features mentioned in different claims, may
possibly be advantageously combined, and the mentioning of these
features in different claims does not exclude that a combination of
features is not possible and advantageous.
* * * * *
References